According to the National Enquirer, Kris Humphries is ignoring that 30-page prenup requiring him to keep his mouth shut about Kim’s silicone loaded butt.

KIM KARDASHIAN’s big booty is a big, fat fake, sources say – and her estranged hubby KRIS HUMPHRIES is threatening to expose the truth!

The reality TV sexpot insists her bubble butt is all natural . . . But some insiders claim the curvy 31-year-old beauty uses butt pads and say Kris filmed a video that proves his estranged wife’s prized posterior is phony!

Kris remarked to pals that, while he loves Kim’s shapely butt, it’s not the same as what you see on the red carpet…or TV.

“Kris told his buddies that it takes a lot of work for Kim to make her bottom look as good as it does,” said a source. “He revealed all her secrets – how she uses ‘booty pads,’ Spanx and other things to enhance it. When she takes off the Spanx, the pads and everything else, it’s not the same.

“He knows what the real thing looks like – be­cause he’s recorded it on his cell phone camera!”

The Enquirer suggests this is the real reason Kim cut her Australian trip short, and rushed to Minnesota to meet with Kris and his parents face-to-face.

“She frantically called Kris but that didn’t work,” said the source. “So she hopped a red-eye flight to his parents’ home in Minnesota to talk to him in person.

“I think Kim wants to make sure Kris keeps the secrets about her body to himself – and NEVER, ever releases the film footage he has of her.”