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BRITNEY BARES TORMENT

Britney Spears admits her marriage was a mistake – and she’s itching to be paroled from her “controlled” life.

“I think I married for the wrong reasons,” the stability-challenged pop tart says of her doomed three-year marriage to Kevin Federline. “Instead of following my heart and, like, doing something that made me really happy, I just did it for the sake of the idea of everything.”

Spears, 26, makes the candid comments in the upcoming documentary, “Britney: For the Record,” which debuts on MTV and Britain’s Sky1 this month. Portions of the film were released yesterday.

POP VIDEO QUIZ: Britney and Friends

Spears also revealed that she’s been merely “existing” since her head-shaving, public mental meltdown, which led to her losing custody of her kids, and her dad, Jamie, gaining control of her affairs.

“Even when you go to jail, you know there’s the time when you’re gonna get out,” the singer mused on camera. “In this situation, it’s never-ending.

“It’s just like [the movie] ‘Groundhog Day’ every day.”

The 90-minute documentary was produced by Spears’ longtime manager, Larry Rudolph.

Cameras followed the singer for three months in her post-breakdown days, in what she said was “an opportunity to set the record straight.”

The flick debuts Nov. 30 as part of a publicity push leading up to the Dec. 2 release of her new album, “Circus.”

The refurbished star is slated to top off the promotion with an appearance at NBC’s Rockefeller Center tree lighting on Dec. 3.

jeane.macintosh@nypost.com