Britney Spears has finally come clean about her relationship with Justin Timberlake, admitting that she did have sex with the US pop sensation.

Spears, who once famously declared she did not believe in sex before marriage, made her not-very-shocking revelations in a recent interview with W magazine.

"It was two years into my relationship with Justin. And I thought he was the one. But I was wrong," she said.

"The most painful thing I've ever experienced was that breakup. We were together so long, and I had this vision. You think you're going to spend the rest of your life together."

She added: "Where I come from, the woman is the homemaker, and that's how I was brought up - you cook for your kids. But now I realise I need my single time. You have to do your own thing."

Doing her "own thing" in recent months has meant working on her new album, and enlisting the likes of Moby and P Diddy as collaborators.

"She did spend some time with them," said a spokesperson at Jive Records, "but we're not even sure if those tracks are going to be picked."

Speaking to W, Moby described his track with the pop princess as "brooding and atmospheric".

"It's very simple and, for lack of a better word, sexy," he said.

Britney's as-yet-untitled fourth LP features additional production work from Rodney Jerkins, The Neptunes, Matrix, 7 Aurelius, Metro, RedZone and Limp Bizkit star Fred Durst.

According to MTV, Spears will continue work on the album for the next two to three weeks before finalising a tracklisting. The album is expected to be released by October.