MARIE OSMOND is devastated after a stunning betrayal by her brother DONNY, who sources say double-crossed her for cold hard cash!

The showbiz legends have been slapped with a shocking lawsuit that claims they fired their Las Vegas producer and stiffed their management agency in a bid to fatten their own bank accounts.

But sources close to the stars insist Marie,51, wasn’t in on the scheme and is a victim of her 52-year-old brother’s greed.

"Marie is heartsick," an insider told The ENQUIRER. "She feels Donny stabbed her in the back for a buck.

"She gives 100 percent while she’s on stage, but she leaves the deal-making to Donny. She trusted him, and now his money-hungry behavior has landed them in court. Marie has told Donny that she hates that he did this to her."

According to a lawsuit filed in Nevada’s Clark County District Court, impresario Chip Lightman claims he negotiated the Osmonds’ deal to perform at the Flamingo Las Vegas Hotel.

But when it came time to extend their contract after a wildly successful two-year run, Donny acted in an "underhanded, devious, fraudulent and greedy" manner, according to the suit.

During his run at the Flamingo, Donny "lived from paycheck to paycheck, scraping by to cover his expenses," according to the suit. So in a bid to save money on commissions, he tried to cut out both Lightman and the William Morris Agency while negotiating an extension, the suit alleges.

"The clear goal of his actions has been to line his own pockets with ill-gotten gains to fund his lavish lifestyle of exotic cars, luxury hotel suites and private jets – all off the backs and hard work of those who worked tirelessly to support his career," the document states.

Marie is also targeted in the lawsuit, which states: "Despite Marie’s seemingly innocent nature, she too is liable for the fraud perpetrated by Donny through her acquiescence, awareness and utter failure to disclose" his actions.

When contacted by The ENQUIRER, Lightman said he’s enjoyed his long relationship with the Osmonds until now and was "blindsided by Donny."

A publisher has contacted him to write a tell-all book about Donny and Marie, he said, "but that’s not something  I would do."

Despite that, the insider pointed out: "If anyone had juicy dirt to spill on Donny and Marie, it would be Chip."