Dirty Dave Letterman’s $400 Million Divorce!

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Cranky talk show host DAVID LETTERMAN is ready to leave television – and his wife!

The “Late Show” host will face an ugly custody battle when he socks his long-suffering wife with a $400 million divorce, sources have told The National ENQUIRER.

Dave, 68, and wife Regina Lasko, 54, have been leading separate lives since his affair with a blonde assistant made headlines in 2009, as The ENQUIRER reported.

Now, Dave “has basically checked out of the marriage,” and plans to leave the mother of his only child, 11-year-old Harry, a source revealed!

“Dave prefers solo jogs on country lanes around his New York country estate to spending time with Regina. Now that he’s set to retire, he’s even more determined to pull the plug,” said the insider.

The couple hasn’t been out together since a Kennedy Center event in December 2012.

Said a source: “It’s been a loveless marriage for years.

“But the final nail in the coffin came when Dave confessed to sleeping with several female staff members, including a torrid affair with Stephanie Birkitt.

“Regina was fit to be tied. She’s never been able to move past the sense of betrayal.”

Dave’s affair with Stephanie, now 40, came to light after her onetime live-in lover, “48 Hours” producer Robert “Joe” Halderman, tried to extort $2 million from the TV host.

Dave confessed to the affair just months after he wed Regina, following a 20-year relationship.

The intensely private TV host addressed the scandal twice on his show in October 2009, first admitting that he’d had sex with several female employees, and then apologizing to his wife and staff.

“The marriage never recovered from the scandal, and appears irretrievably broken,” added the first source.

“Now the focus is on who gets Harry, and how much Dave will have to shell out to his bitter wife. There will definitely be a custody tug-of-war. And it could be a downright dirty battle.”

While Dave’s spokesman said rumors of a split are “completely untrue,” Regina spends most of her time at Dave’s sprawling estate in rural North Salem, N.Y.

He also owns a loft in Manhattan, which one neighbor told The ENQUIRER could be his “love nest” after seeing Dave there with a blonde woman who wasn’t his wife.

Dave – who’s been a TV fixture since “Late Night with David Letterman” debuted on NBC on Feb. 1, 1982 – also owns a 2,700-acre ranch outside Choteau, Mont.

He moved to CBS in 1993, and after his run there ends on May 20, Dave intends to spend more time at the ranch, and he wants Harry at his side, added the first source.