Sir Paul McCartney says he'll retire when he ''feels like it''.

The 'Hey Jude' singer has had an iconic career, but he insisted he is constantly learning new skills, which means he has no plans to call it quits just yet.

The rocker has recalled an early show when The Beatles were still known as The Quarrymen, and he messed up his big moment as he stepped forward to take on lead guitar duties.

He told Rolling Stone magazine: ''I don't even think we were The Beatles, it was the Quarrymen ... and I had a lead solo in one of the songs and I totally froze when my moment came.

''I really played the crappiest solo ever. I said, 'That's it. I'm never going to play lead guitar again'. It was just too nerve-wracking onstage.

''So for years, I just became rhythm guitar and bass player and played a bit of piano, do a bit of this, that and the other. But nowadays, I play lead guitar, and that's the thing that draws me forward. I enjoy it. So, yeah, that means the answer to 'Are you going to retire?' is 'When I feel like it'. But that's not today.''

Paul, 72, admitted he was once told by a manager he should retire when he was 50, but he quickly dismissed the idea - and has now claimed The Rolling Stones prove why he can keep going.

He added: ''I thought about it for a second and thought, 'Nah'. When will you give up? When will it give out? Who knows? But the margin has been stretched these days.

''The Stones go out now, and I go to their show and I think, 'It doesn't matter that they're old gits. They can play great'. And I talk to young kids who say exactly the same thing: 'They play good.' ''