Bottom's up for Keira Knightley

Keira Knightley has confessed she used a bottom double for her new movie - because her butt was out of shape

She revealed: "I'd just finished 'Pride and Prejudice' and I hadn't had a chance to train

"I couldn't actually lap dance very well

I did the top half, but a girl called Tarin did the bottom

" The sexy star added in an interview with Britain's Sunday Times Style magazine: "Another girl appeared in the paper saying it was her, but I'd never seen in my life

I'm sure she's got a great arse - but not in my film

"Meanwhile, Keira has confessed how she had to beg to get a role in her next movie.

The beautiful star, who plays a down-on-her-luck young woman in upcoming film 'The Jacket', confessed: "All the girls I've done have been quite nice girls, but nobody's just a nice girl, nobody's just a horrible girl."The director didn't want me for the part. He thought I was completely wrong.

"I begged him, 'Please let me read, because otherwise I'm going to be stuck in corsets for the next 20 years'".