Kidman has revealed how she transformed herself into what one critic described as a "hot, over-sexed Barbie" for her role in Cannes competition entry The Paperboy. Kidman plays a woman in the Deep South who writes to prisoners on Death Row and falls for a lecherous convicted killer, played by John Cusack.

The pair have two risqué sex scenes together and Kidman also ends up in bed with Efron, an actor 20 years her junior.

Her character, Charlotte Bless, wears a succession of eye-popping outfits and teeters through the film in high heels, a platinum blonde wig and enormous false eyelashes.

To create her trashy look, Kidman, 44, raided her own make-up bag.

Recalling her initial discussion with director Lee Daniels, Kidman explained: "Lee said: 'Look, we've got no money, you're going to have to do your own hair and make-up.'

"So, I actually went into my bathroom and I got out the fake tan and put on fake eyelashes and got a hairpiece thing that was platinum, threw it all on and texted a photo to Lee in all these different provocative positions. That's how it came together."

She said she had been seeking a change of direction in her career by choosing more daring roles, and Charlotte Bless fitted the bill.

"I've been looking as an actor for something raw and more dangerous in terms of performances, and then this came along," she said.

"I don't want to ever be pigeon-holed, to be thought of as: 'You can't be in that kind of genre.' I'm willing to fail, but I want to be given a chance to try."

The film is directed by Daniels (Monster's Ball and Precious) and based on a novel by Pete Dexter.

To research the role, Kidman met a group of women who wrote to prisoners on Death Row.

"I sat down in a room with five women who were all in love with men in prison. They told me stories that were like - wow."

Efron, the former teen heart-throb, said he was thrilled to have a love scene with Kidman.

"I had the most lovely time in the world. I was ecstatic the day I found out she was playing the part," the actor said.

"I have been in love with her for a long time, since Moulin Rouge. It was the best opportunity in the world for me and I loved every moment."