Britney Spears says marrying Kevin Federline was a mistake.

The 26-year-old singer — who has two sons, three-year-old Sean Preston and two-year-old Jayden James, with Federline — wishes she had never walked down the aisle with the former backing dancer.

In a promo for her new documentary 'Britney: For the Record', Spears said: "I think I married for the wrong reasons. Instead of following my heart and doing what made me really happy, I just did it for the sake of the idea of everything."

In the advert, which is accompanied by Spears' new track 'Womaniser', she said her split from Federline has influenced her music.

She said: "Your music is a reflection of what you're going through. It's such a part of me, the record, because of what I’ve gone through."

Spears and Federline married in September 2004 and split in summer 2006. Their divorce was finalised in July 2007.

Meanwhile, Spears sparked rumours she has a new boyfriend after she was photographed leaving a Los Angeles restaurant with a mystery man on Monday night.

The dark-haired man has now been identified as Salvatore D'Angelo, the manager of Spears' favourite hairdressers, Kim Vo's B2V salon.