Keira's pasta and wine diet

The 21-year-old also admits she has not visited a gym in six months.

"I'm not one of those people who's going to jog five miles every morning," she says.

"I'm trying to go 'F*** it' and have bowls of pasta or whatever makes me happy," she says. "I haven't been to the gym since January and I'm drinking about half a bottle of wine a night.

She adds: "F*** it, you've got one life - live it."

The 5ft 8in star, who says she is a size 10 on top and 12 on the bottom, envies the curves of Scarlett Johansson and Kate Winslet.

She says: "That kind of decadent flesh is absolutely beautiful. How sexy is that on a woman?"

She claims she is so careless about her appearance she even forgot to shave her legs for the Vanity Fair cover, in which she appeared naked with 21-year-old Johansson.

"I thought, 'It's the cover of Vanity Fair, I'm 20, it's now or never'. I hadn't shaved my legs but everyone was all right with that.

"We kept looking at each other and then eventually we went [mimes wiggling out of a robe] at the same time. We had such a laugh. Scarlett's a sweetheart. "I'm not completely comfortable with my body but I just thought, 'F*** it'."

Despite being the new face of Chanel's Coco Mademoiselle, the actress tells Elle magazine her top beauty products are E45 cream and witch hazel.

Although she can turn on the red carpet glamour, Knightley adds: "When I'm not working I'll put a dress on and think, yeah, that looks great. But then I'll feel a dickhead so I put my jeans on." She also reveals the reason she donned a pig mask to leave her 21st birthday party earlier this year in London - she got "annihilated" by alcohol.

"My make-up was smeared round my face, so I put on a pig mask to leave," she explains.

Knightley swears like a trooper - and even makes beaded jewellery for her friends and family emblazoned with fourletter insults. "I put c***," she reveals. "I did one for my brother that said f*** w**k and I do dickhead, too."

Knightley is also decidedly frank when discussing her recent successes.

Of her Oscar nomination for Pride And Prejudice, she says: "I knew I didn't have a hope in hell - my dad went to the bookies and the best odds he could find were 33-1. He put a fiver on, anyway!"

But Knightley and her brother Caleb, 27, got to sit next to Jack Nicholson - "a true f***ing Hollywood moment".

Keira Knightley's new film Pirates Of The Caribbean: Dead Man's Chest is released on 6 July.