Britney Spears Celebrates 27th Birthday With Heidi Klum...And A Nipple Slip

Britney Spears' breasts made a bid for freedom during her birthday celebrations yesterday.

The star showed off her recently-regained svelte figure at a party thrown for her at NYC club Tenjune to mark the release of her new album and her 27th birthday.

But the Piece Of Me star's figure-hugging designer dress left too little to the imagination as it struggled to contain her famous curves.

A worried Britney had to hitch up the straps as her outfit began to slip down and reveal a lacy black bra...and a hint of nipple.

Other stars that turned up to toast Britney included supermodels Heidi Klum and Alessandra Ambrosio, and former NSYNC-er Lance Bass.

See her nipplegate scandal below