Carey Mulligan has never taken drugs.

The 'Wall Street: Money Never Sleeps' actress has no interest in illegal substances, and doesn't think she'd be prepared to experiment for a movie role even if it was a great part.

She said: "I've never done cocaine or anything, and I've never played a character who has, so I don't know whether I would actually try coke if I had to play a character who took coke. It's never come up before. But I don't like the idea of having to mess yourself up to be a good actor.

"I feel like there's a switch in your head that you're required to turn on and off more often when you're making a movie. I haven't done this long enough to identify what it is, but I do find it easier to turn the switch on in theatre than in film."

The 24-year-old star wants to throw herself into a wide range of roles, and is grateful she finds it easy to alter her appearance.

She explained to Interview magazine: "Luckily, I'm not restricted when it comes to age. I can play a bit younger, like I did in 'An Education', but I can also play older, like I did in 'Never Let Me Go', where my character is 28 by the end of the film. I also don't look specific - I can change my appearance quite easily just by changing my hair. So I can adapt quite well."