Spain's King Juan Carlos wanted to abdicate because he didn't want his son "withering" like Britain's Prince Charles waiting to take the throne.
The 76-year-old monarch, who announced last week that it was time for a "younger generation to step into the front line", reportedly told courtiers that he wanted to abdicate because he didn't want to see his son, Prince Felipe, "grow old waiting for the throne like Prince Charles".
Charles, 65, is the oldest heir to the British throne for 300 years, with his mother Queen Elizabeth now 88.
Juan is believed to have been considering stepping down since his 75th birthday because he wanted his son to be in charge when he was still a young man.
He reportedly spoke to Rafael Spottorno, chief of the royal household, and said: "I do not want my son to wither like Prince Charles," according to Spain's El Mundo newspaper.
The Zarzuela Palace refused to confirm or deny the statement and a Clarence House spokseman "declined to comment" on the reports.
Meanwhile, John Prescott, the former Deputy Prime Minister, has called for the Queen to "gracefully step aside" and allow Prince Charles to deliver next year's address to Parliament.

George Clooney is planning to marry in Venice.
The 'Monuments Men' actor and human rights lawyer Amal Alamuddin - who got engaged in April - are to tie the knot in Italy in September and decided against holding their wedding at his Lake Como estate because they felt it wasn't private enough.
A source told the New York Post newspaper's Page Six column: "George and Amal want to be married in Italy, but they need a location that offers them and their guests privacy."
George - who also didn't want to inconvenience his Lake Como neighbours with the attention his wedding would bring - and Amal were seen dining in Venice a few weeks ago after touring wedding venues and are said to be planning to marry at a palace in the city.
The pair visited Venetian restaurant Da Ivo along with the 53-year-old actor's bodyguard and his girlfriend, and they enjoyed a feast of sautéed shellfish, smoked tuna, mussel soup, crayfish and artichoke risotto and charcoal-grilled seabass accompanied by Prosecco and white wine.
The next morning, they flew out of Venice airport by helicopter.
It was recently claimed the couple had been considering marrying at Highclere Castle - the Hampshire estate where 'Downton Abbey' is filmed - but had a change of heart after Amal learned British ex-glamour model Katie Price had tied the knot there with first husband Peter Andre in 2005.
A source said: "Amal doesn't really know that much about celebrity.
"But she is well aware who Katie Price is and didn't want her big day to be in any way associated with that kind of media circus.
"So they've gone back to the drawing board and are looking at other places."

Olly Murs is planning to propose to his girlfriend.
The 'Heart Skips a Beat' singer is smitten with model Francesca Thomas - who he began in August 2012 - and after turning 30 last month, he thinks now is time to settle down.
A source said: "Now Olly has turned 30, he's realised he's ready to settle down.
"He's told all his friends that he's planning the perfect proposal."
The 'Troublemaker' singer had dated Francesca, 25, for over a year before their romance became public and Olly - who shot to fame after coming second on 'The X Factor' in 2009 - has since admitted he deliberately kept the relationship hidden to allow it chance to "blossom".
He said: "Now everyone knows I have a girlfriend, but being in the public eye can ruin everything.
"It'd be different if I was dating a celebrity but I want to give this a chance to blossom - and being in the industry makes it a hundred times harder.
"I don't think my fans will be upset - if each member of One Direction can have girlfriends and be OK, I'm sure I can."
Olly has also admitted to having had a string of secret romances since finding fame.
He said: "I've been dating girls the whole time. In four years, there haven't been any stories about me.
"People even questioned my sexuality because of it."

Bryan Cranston has won a Tony Award for his Broadway debut.
The 'Breaking Bad' star picked up Best Lead Actor in a Play for his role as former President Lyndon B. Johnson in Robert Schenkkan's 'All The Way', beating the likes of Chris O'Dowd in 'Of Mice and Men' to the title.
The multiple Emmy award winner, best known for playing chemistry teacher-turned-drug lord Walter White, scored his first ever theatre prize as 'All The Way' was also crowned Best Play.
Audra McDonald made history by winning her sixth Tony for her performance as Billie Holiday in 'Lady Day at Emerson's Bar & Grill', becoming the only woman to win a Tony in all four acting categories.
She said in her emotional acceptance speech: "I want to thank all the shoulders of the strong and brave and courageous women that I am standing on. And most of all Billie Holiday. You deserve so much more than you were given when you were on this earth."
Meanwhile, British actress Sophie Okonedo was given the Featured Actress in a Play prize for her Broadway debut as Denzel Washington's wife in 'A Raisin in the Sun'.
She enthused, "I am loving it on Broadway", while the play also won best revival.
The ceremony was hosted by Hugh Jackman at Radio City Music and boasted performances by Tony nominated singer Idina Menzel, Gladys Knight and the cast of 'Cabaret'.
The 'Les Miserables' actor, who was hosting for the first time in nine years, joined the cast of the musical 'After Midnight' for a rendition of 'It Don't Mean a Thing (If it Ain't Got that Swing)'.
Another highlight from the ceremony was Neil Patrick Harris - who scooped the Best Actor in a Musical gong - performing a song from 'Hedwig and the Angry Inch', dressed in a miniskirt and blonde wig.
He got into character by giving an audience member a lap dance and even confiscated Samuel L. Jackson's glasses and licked them.

The full list of 2014 Tony Awards winners:

Best Play: 'All the Way'
Best Revival of a Play: 'A Raisin in the Sun'
Best Revival of a Musical: 'Hedwig and the Angry Inch'
Best Book of a Musical: 'A Gentleman's Guide to Love & Murder'
Best Performance by an Actor in a Leading Role in a Play: Bryan Cranston, 'All the Way'
Best Performance by an Actress in a Leading Role in a Play - Audra McDonald, Lady Day at 'Emerson's Bar & Grill'
Best Performance by an Actor in a Featured Role in a Play: Mark Rylance, 'Twelfth Night'
Best Performance by an Actress in a Featured Role in a Musical: Lena Hall, 'Hedwig and the Angry Inch'
Best Performance by an Actor in a Leading Role in a Musical
Neil Patrick Harris, 'Hedwig and the Angry Inch'
Best Direction of a Musical: Darko Tresnjak, 'A Gentleman's Guide to Love & Murder'
Best Direction of a Play: Kenny Leon, 'A Raisin in the Sun'
Best Score: Jason Robert Brown, 'The Bridges of Madison County'
Best Performance by an Actor in a Featured Role in a Musical: James Monroe Iglehart, 'Aladdin'
Best Performance by an Actress in a Featured Role in a Play: Sophie Okonedo, 'A Raisin in the Sun'

Sir Mick Jagger's new romance is a "fling".
The 70-year-old music legend - whose longterm girlfriend L'Wren Scott committed suicide in March - was spotted cosying up to a younger woman in Zurich, Switzerland, last week, but a friend has defended him, insisting he needs to move on with his life.
The close pal said: "Of course Mick is still sad over L'Wren but he is working through it and trying to move on with his life. Yes, he had a fling - he's a red-blooded man for goodness sake. But it's nice to see him enjoying life again. He's on the mend."
Meanwhile, Mick recently returned to the stage with the Rolling Stones but the group omitted their 1966 song 'Paint It Black' - about the death of a lover - from the set list for their first three gigs because it's still highly emotional for the musician.
The haunting track sees the rocker describe a funeral, singing: "I see a line of cars and they're all painted black, with flowers and my love both never to come back."
A source told the Daily Mirror newspaper: "The lyrics are very personal to Mick and he didn't feel comfortable singing them so soon after L'Wren's death."
Following the publication of pictures of the 'Brown Sugar' star and the mystery brunette, L'Wren's sister Jan Shane blasted the rocker.
She said: "And people wonder why L'Wren was so depressed?
"These pictures make me really wonder what Mick is thinking and feeling. His daughter says that he is still heartbroken and so devastated about losing my sister.
"And then you see these photos. He will never change."

Marc Baylis is relieved Rob Donovan has been outed as Tina McIntrye's killer.
The 'Coronation Street' actor has spent months keeping quiet about the ITV soap's biggest storyline of 2014, so couldn't wait for his dramatic scenes to finally air last week.
Rob shocked viewers by throwing Tina (Michelle Keegan) from the builders' yard balcony after she threatened to reveal his all his secrets and ruin his sister Carla's marriage to Peter Barlow, with whom she was having an affair, but Marc claims the drama is far from over.
He enthused: "It's a massive relief! I've known about this storyline since November, and the only person I told was my girlfriend. I didn't even tell any of my family because I didn't want to ruin it for anyone!
"This is not the end of the storyline - it's the beginning of a new chapter for Rob, and for the Street. There are a lot of ramifications to come, with plenty of twists and turns."
The 37-year-old star hinted Rob might let someone else take the blame when the police question Peter and Carla about Tina's murder.
Marc teased: "It's all about the aftermath and how Rob deals with it. Who gets framed for the deed itself? Would he let someone else take the blame? Well, it depends who that person is!
"But he would never let that happen to Carla. The only reason he went to see Tina was that he was trying to protect his sister."
The actor is worried about the British public's reaction to the showdown, but is focused on making the coming months as exciting as possible.
He added in an interview with InsideSoap magazine: "I know, I can't walk down the street anywhere in the UK now! I haven't had enough time to worry about anything though. Rob will have to move on at some point, but there's months of drama ahead before that."

One Direction have thanked their fans for an "unforgettable" weekend of gigs at Wembley Stadium.
The 'Midnight Memories' hitmakers performed their third consecutive date at the London venue last night (08.06.14) as part of the 'Where We Are Tour' and were overwhelmed by the reaction from fans after they played to about 80,000 people each night.
Louis Tomlinson took to Twitter to tell fans he and how grateful he was for the opportunity to play the iconic venue.
He posted: "We will never forget this weekend ! Thank you so much for making it happen. Eternally grateful !! (sic)"
Harry Styles also tweeted: "Thank you so much Wembley. To everyone who spent their evening with us... You were on another level. Thank you for having us .x (sic)"
According to the Daily Mirror newspaper, the band - including Liam Payne, Niall Horan and Zayn Malik - had the audience singing along last night to their hit 'Little Things' and Liam said: "That was the loudest 'Little Things' sing along ever."
He added: "I can't believe I'm in Wembley stadium in the middle of the pitch.
"If there was a moment I could bottle forever, this would be it."
All the boys have been gushing about their performances at the venue, which are their biggest gigs to date, and Niall previously tweeted: "Wembley was just out of this world last night ! everything about it was great! Can't wait t do it all again tonight ! (sic)"
Meanwhile, Zayn, 21, and Louis, 22, are trying to get past their recent drugs drama after being filmed smoking a cannabis-laced cigarette while on tour in Peru.
The pair were seen joking about drugs and being caught by the police in the back of a bus.

Girls Aloud weren't "rock 'n' roll" enough for drugs.
The best-selling girl band - who called it quits last year after their 'Ten: The Hits Tour 2013' - were never interested in taking illegal substances and former member Kimberley Walsh is grateful their careers weren't marred by the party lifestyle.
She exclusively told BANG Showbiz: "We're not that kind of group. We weren't really very rock 'n' roll - which people don't want to hear because it's a little bit dull! We're not partiers, we don't go to clubs that play the kind of music that goes with drugs and we're kind of chilled out.
"It never really was an issue for us, which is lucky because that can often be the one thing that does completely break down the group. That was a blessing, definitely, that we were not those kind of girls."
Kimberley - who is expecting her first child with her partner of over 10 years, Justin Scott - believes being surrounded by family and friends who knew her before she shot to fame in 2002 helped her stay grounded during the band's heyday.
She explained: "People have always got quite wrapped up in that lifestyle, it's an easy thing to happen. It just depends on who you are as a person and what your surroundings are like. I have a lot of family and friends that have always been there, ever since I was thrown into a weird environment.
"I've always had that security around me so that's probably why it's a little bit different for me. It depends on your type, some people find it tough."
With her new arrival due in September, Kimberley is already thinking about future careers for her child and the potential pitfalls of a showbiz lifestyle.
She mused: "I wouldn't particularly encourage it because it's a really tough business to be in. But at the same time, I'd never deny them their passion because nobody denied me mine.
"I think you know straight away what kind of child they are and will push them in the direction that's going to be best for them."
Kimberley's new duet with Alistair Griffin, 'The Road', is out now via Elbow Grease Records. The video for the single can be seen on Youtube.com and Alistair releases his new album 'From Nowhere' on July 7.

Mark Ronson likes Lily Allen's honesty.
The 38-year-old star collaborated with the 'Hard Out Here' hitmaker on their 2007 single 'Oh My God' and has since maintained a close with relationship with her, claiming that her ability to tell the truth is what makes her music so successful.
Quizzed about what his opinion of Lily's new album 'Sheezus' was, he said: "It's great. I think Lily has a way of telling it like it is. She's so honest and that's what strikes me about her."
While Lily, 29 - who has daughters Ethel, two, and 17-month-old Marnie with her husband Sam Cooper - is an avid user of social media sites such as Twitter and Instagram, Mark admits he's not as keen and doesn't even have a smartphone.
When asked if he keeps up to date with Lily's posts, he admitted: "I'm not really interested in all that. I have, like, an old Nokia phone!"
Mark - who is married to French actress Joséphine de La Baume - also spoke about his family life and admitted that although growing up with lots of siblings was hard, he feels lucky to have had their support.
Speaking about whether family life was important to him, he told BANG Showbiz: "I have 9 brothers and sisters so I don't have much of a choice. All families have arguments but you've just got to get on with it and appreciate what you have."

Kirsten Dunst wants to work with Judd Apatow.
The actress made a name for herself with comedies like 'Bring It On' as a teenager and after years of cutting her teeth on more serious dramas, she feels ready to make a comedic return.
However, the 32-year-old star wouldn't work with just anyone and has set her sights on top Hollywood funnyman Judd, the man behind 'Knocked Up' and 'The 40-year-old Virgin'.
Asked whether she wanted to make more comedies, she replied: "Yes, but it all depends on the director. A comedy needs a lot of effort, it's much harder than it looks. I think I'd like to make a film with Judd Apatow."
Kirsten also has a number of other A-list directors on her wish list to work with.
She told French magazine Madame Figaro: "Michael Haneke, to start with: he's got a magnificent style and knows how to shoot actresses. And I speak German, so hopefully it would be an advantage! And also Quentin Tarantino."
The blonde recently made a brief return to comedy opposite Isla Fisher in 'Bachelorette' and she credits her wide range of roles for keeping her career going.
She explained: "There is no secret: everything depends on the choices you make. And the people you surround yourself with. If you work with the right people, you progress and keep going. It's up to you.
"Do you know how many roles of depressive women I was offered after 'Melancholia'? Luckily, I made 'Bachelorette' just after, which pushed me in a new direction."

Kourtney Kardashian has confirmed she's pregnant and admits the baby was unplanned.
The reality star and her long-term partner Scott Disick, who have children Mason, four, and Penelope, 23 months, are expecting their third child together in December.
Kourtney confirmed she is expecting during a premiere episode of 'Keeping Up With The Kardashians' on E! last night (08.0.14), which saw the brunette beauty, 35, tell Scott the exciting news.
She said: "I'm pregnant," adding, "It was not a plan."
The announcement was saved for the end of the episode in a montage of clips showing viewers what would be coming up on the reality show later on in the season.
The star is currently filming the spin-off show 'Kourtney & Khloe Take The Hamptons' with sister Khloe Kardashian and their mother and other sister Kim had both teased fans that the pregnancy rumours would be discussed on Sunday's show.
Kim wrote on Twitter: "Kourtney will also be addressing pregnancy rumours this Sunday on our premiere!," adding "So be sure to tune in! #keepingupwiththeKardashians. (sic)"
Kourtney and Scott, 31, have been together since 2007 and their famously tempestuous romance is publicly documented on the Kardashian family's numerous reality shows.
Us Weekly broke the news that Kourtney is expecting her third child last week and a source claimed she wants to have "a handful of kids."
The insider said the star was "only a few months along" and has abstained from drinking since finding out the news.

Rita Ora is being comforted by one of Justin Bieber's friends after splitting from Calvin Harris.
The 'I Will Never Let You Down' hitmaker's DJ ex-boyfriend confirmed their break-up on twitter last week after an on/off year-long romance and the beauty has been enjoying the company of singer Khali Amir Sharieff, who was arrested alongside Justin for drag racing earlier this year.
A source told The Sun newspaper: "Rita was a little mortified that Calvin tweeted about the split but she's just getting on with things.
"She has been with Khalil but who knows how long it will last?"
Calvin, who tweeted that the pair had gone their separate ways "some time ago" but wished her "all the best" in the future, was happy to be seen photographed leaving Hooray Henry's in Los Angeles with a group of ladies at the weekend, while Rita has been living at the new London celebrity haunt Chiltern Firehouse for the past few weeks.
The source added: "A lot of things worked against her and Calvin, such as distance and hectic work schedule.
"And Rita is a self-admitted party girl. She likes to have fun and sometimes she can be hard to keep up with -- not that there's anything wrong with that."
It has also been rumoured that Justin was the reason behind their break-up after she got close to him in the studio.
Meanwhile, Khali, who signed to Def Jam records in 2008, has insisted in the past that he's all about the music and doesn't want to get himself in trouble, despite his arrest.
He said: "I'm not too much of a wild guy. I'm all about work, I'm all about studio. A lot of different things I do keep me stable."
Rita, 23, and Calvin, 30, were last spotted together at Radio 1's Big Weekend in Glasgow where they both performed and Rita even watched from the side of the stage as Calvin took to the decks.