The colourful singer is seen grabbing her chest as the wardrobe malfunction occurs.
The saucy scene is taken from a short web teaser for the promo to her latest song Last Friday Night.
In the eighties-inspired clip, the singer, 26, portrays a fictional character called Kathy Beth Terry.
At one point she even vomits into a rollerskate.
Elsewhere in the clip she is seen sporting ugly braces and nerdy glasses.
Its arrival comes shortly after the government outlined plans to ban raunchy pop videos from being shown on TV before 9pm.
Clips where pop stars flaunt their sexuality are also to be given cinema-style age certificates under new plans.
And curvy Katy, like fellow racy divas RIHANNA and CHRISTINA AGUILERA could come a cropper due to their fondness for outrageous outfits.
On her current Teenage Dream tour she sports a series of sexy outfits that could flout regulations.