Billie Piper's underwear is nearly 20 years old.

The 'Collateral' actress may look glamorous on the red carpet, but she admitted that underneath her dresses, her lingerie never matches.

She said: ''I mean, who has a flesh-coloured slip on hand? I haven't got that wardrobe -- my bras are from when I was 16 and my pants have all got holes in them.''

The 35-year-old star - who has two sons, Winston, nine, and Eugene, five, with ex-husband Laurence Fox - also admitted she is starting to think she should dress more modestly.

She told the Sunday Times Style magazine: ''I'm just at that point where I'm thinking, am I mutton dressed as lamb? Should I be showing my knees?

''There's this bulge of skin that doesn't stay up any more, and although the modern world tells me to celebrate that, I don't f***ing wanna!''

Billie's new TV show, 'Collateral', was written by David Hare and not only did they bond straight away, but she's a big admirer of his sense of style.

She said: ''He's louche and has a wicked sense of humour. I love the way he dresses, too, like a poet, with his brogues and his scarves, and the way that he can cross his legs a few times over.''

The 'Because We Want To' hitmaker has previously spoken of how she developed an eating disorder and considered suicide at 16 because of the pressures of her pop career, and she admitted being ''oversexualised'' at such a young age made her favour baggy clothes for a long time.

She said: ''The oversexualised years. I think that's why, for so long, my desire to hide my body in baggy clothes took hold. I like girl's clothes now because I feel in a better place, but the hangover from that time lasted a while.

''I think I'm in a good place now, or, at least, a juncture.''