James Corden really wanted to sing in the new Paul Potts biopic 'One Chance'.

The actor will be seen playing the 'Britain's Got Talent' winner on the big screen in a movie documenting his rise to stardom, but he has revealed he was forced to lip-synch during musical scenes because his vocal ability wasn't strong enough.

Speaking at the premiere of 'One Chance' in Leicester Square, London, last night (17.10.13), he told BANG Showbiz: ''I wanted to sing, but I had a meeting with our producer and he said someone else should do that. Apparently there's a big leap between singing and singing opera. It became very obvious very quickly that I wasn't able to sing quite as well as they needed.''

The biopic - which was directed by 'The Devil Wears Prada' helmer David Frankel - co-stars Julie Walters and Colm Meany as Potts' parents, Alexandra Roach as his wife Julie-Ann Cooper, and the film will also feature cameos from 'Britain's Got Talent' judges Simon Cowell, who is one of the film's producers, and Amanda Holden.

The 35-year-old comedian admits he's always been a fan of Walters, but since working with her on the movie he's developed even more admiration for her because of her laid-back personality and commitment.

He explained: ''I'm such a huge fan. I always have been. I remember me and my sister used to watch 'As Seen on TV with Victoria Wood' all the time, it's brilliant. The greatest thing about her is she doesn't let you down. You just go away loving her even more than you did. She takes the work really seriously and doesn't take herself seriously at all. That's the best type of person.''