Britney Spears has revealed she got hitched to Kevin Federline for the "wrong reasons".

In her forthcoming documentary for MTV, the pop star admitted: "Instead of following my heart and doing what made me really happy, I just did it for the sake of the idea of everything."

Britney married Federline in 2004, following a whirlwind relationship. The ex-dancer currently has sole custody of their two sons, Sean Preston and Jayden James, after Britney suffered a series of public breakdowns.

The 26-year-old also said she's "grown up, big time", and expressed regret for her past behaviour.

"Sometimes it can get lonely because you don't open the gate," she said. "I'm stuck in this place and I just cope every day. I sit there and look back...I'm a smart person, what the hell was I thinking?"

The singer will release her sixth album, Circus, on December 2, The MTV documentary, For The Record, will air on November 30.

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