DAVID LETTERMAN is embroiled in a divorce shocker that could cost him part of his $400 million fortune.

In a bombshell world exclusive, sources tell The ENQUIRER that the edgy host has never been able to repair his marriage following his sensa­tional 2009 sex scandal, when he confessed to sleeping with several female staff members.

Now, five years later, sources are concerned he and his long-suffering wife Regina Lasko – the mother of his 10-year-old son Harry – are living “separate lives,” and fear she’s close to fi­nally ending their painful union.

“I believe Regina’s had it and wants out,” a close source told The ENQUIRER. “But I think she would wait until he ‘retires’ before she hits him with divorce papers so he won’t have to go through another scandal on the show.

“She hasn’t forgiven him for what he did, and it’s destroyed their relationship.”

Meanwhile, David also appears to be miserable.

“His marriage has been like a prison,” revealed an insider. “He and Regina hardly ever go on trips together. In the past two years, he’s taken her out just ONCE publicly – and that was only when he was a Kennedy Center Honors recipi­ent in Washington, D.C.”

Letterman’s representative vehemently denies the fun­nyman has any plans to divorce once he exits “Late Night” in 2015, but confirms that the damage from the star’s sex scandal hasn’t been repaired.

“It’s still an ongoing process,” the rep told The ENQUIRER.

Insiders say Regina, 53, is still reeling from the day David faced the cameras and admitted to millions of shocked viewers that he had sex with several “Late Night” staffers – including an explo­sive affair with his assistant Stephanie Birkitt.

Letterman’s hand was forced because he’d become the victim of attempted black­mail by Birkitt’s one-time lover, “48 Hours” producer Robert “Joe” Halderman, whose $2 million extortion attempt resulted in a six-month jail sen­tence. Incredibly, the entertainer’s bomb­shell confession came just months after he finally wed Regina, following a 20-year-long relationship. During that time, in­siders say Letterman has amassed a stagger­ing $400 million.

“I think Regina is entitled to hundreds of millions after what Dave put her through,” said the close source.

Letterman, 67, has a very successful pro­duction company, ironically named World­wide Pants. It owns his CBS show as well as “The Late Late Show with Craig Ferguson” plus syndicated rights to the popular sitcom “Everybody Loves Raymond.”

Letterman is also said to own more than $75 million in real estate hold­ings and boasts an annual income of more than $45 million.

Despite friends’ divorce concerns, for now David and Regina still stay at their North Salem, N.Y., estate or at David’s Manhattan loft apartment – “I bet he used to use the loft as his ‘love nest’ to cheat on Regina,” a neighbor told The ENQUIRER. “I’ve seen him there recently, with a woman who doesn’t resemble his wife. The woman he’s been seen with is a blonde.”