The 34-year-old - who recently confirmed her engagement to body builder beau David McIntosh - stripped down to her spotty bra and pants, took a snap and posted it to the photo sharing site complete with arty black and white filter.
"Mind the gap #belfie," Kelly wrote alongside the shot and while some of her followers were quick to pull KB up on her "thigh gap" reference - one writing: "You don't need a thigh gap to be hot or attractive." - most seemed to be more concerned with her undies.
"If Kelly Brook can wear these pants so can I," read one comment while most others simply referred to her polka dot pants as "granny knickers" or "Bridget Jones pants".
The snap comes as Kelly's been living it up in Miami with fiance David while filming the pilot episode of sit-com One Big Happy which she landed a leading role in earlier this year.
However, we all know Kelly loves a good Instagram post, so we weren't surprised when just hours later she was sharing a video of her cycling down South Beach, Florida.
"Who are you wearing?" the hidden videographer said from behind the lens, mocking the likes of Ryan Seacrest and Kelly Osbourne who are famed for asking red carpet regulars which designer their outfit of choice is by.
"Today I'm wearing Topshop," Kelly responded showing off her sweet sky blue denim playsuit while grinning from ear-to-ear.
The posts come after Kelly recently trashed rumours she'd coughed up for her own engagement ring. "I'm marrying a very traditional man," she told us. "But there is nothing wrong with women buying there own rings. I just didn't," the model exclusively told MyDaily.
LOVE KELLY? See more from the brunette beauty in the best of her Instagram snaps in the gallery below.