Published on: December 19, 2011
Photography by: Getty Images

PRINCE WILLIAM is secretly in love with his wife’s stunning sister, PIPPA MIDDLETON – and insiders say the explosive scandal could take down the British monarchy once and for all!

Pippa, 28, has been invited to join the royal family at the country estate of Sandringham Palace for Christ¬mas as a guest of William and Kate’s for his younger brother Harry, but royal insiders reveal that it’s all a big sham. They claim it was William who orchestrated the whole affair – just so he can have her around!

What’s more, the insiders claim that William’s pretty wife Kate has no idea her new husband is harboring such deep feelings for her sister, and that if she did, their eight-month marriage would be over.

“William has fallen hard for Pippa. He can’t take his eyes off her,” one insider told The ENQUIRER.

“William is just using Harry as a smokescreen so he can have Pippa close by.”

Sources close to William, 29, divulged to The ENQUIRER that the would-be king often fantasizes about his sexy sister-in-law, marveling: “My God, she’s so beautiful!”

Indeed, the curvaceous brunette nearly stole the show at William and Kate’s April wedding. Pictures of her bending over to adjust the train on Kate’s gown popped up all over the Internet and earned her a legion of admirers worldwide, including her new brother-in-law. “Kate would be beyond furious if she knew what was REALLY going on! This could end up in divorce,” maintained the insider.

“Prince William now realizes he’s had a long, deep-seated love for his wife’s sister.”

Just weeks after the nups, Pippa caused a stir when racy pictures appeared on the Internet.

In one photo, she modeled a minidress made of toilet paper. In another, Pippa wore a purple push-up bra while dirty-dancing with a hunk wearing only boxer shorts.

Duchess of Cambridge Kate, 29, was “outraged,” said the insider, and immediately reprimanded her wild younger sibling.

“But Prince William LOVED the pictures,” insisted the insider. “They were fuel for his fantasies. He’s asked himself time and again, ‘Did I marry the wrong sister?’”

Pippa split from her boyfriend, banker Alex Loudon, 31, early in November – and it appeared that she’d won the heart of Prince Harry, 27.

But the insider insists it was William who saw the breakup as an opportunity.

“If this Pippa thing goes any further it could bring down the monarchy,” warned another source.

“Unless William lets go of his infatuation he could create the biggest royal scandal in recent history.

“Right now Pippa is his fantasy woman. We can only pray he comes to his senses and keeps it that way.”