It's gonna be a tough day for Dave ...and rightly so. He's admitted to cheating on his girlfriend/wife of 20 years by having sex with his female staffers.

Letterman found himself the target of a extortion plot allegedly intiated by Robert "Joe" Halderman, a producer for 48 Hours and boyfriend of a woman with whom Letterman was having sex.

Freaky-deaky, dude.

"...David Letterman told the audience of his late night talk show that he had sexual relationships with female members of his staff, and added he forked over a bogus $2 million check as part of an extortion plot on the matter.

Letterman, 62, made the confessions to the audience during a taping of "The Late Show" for broadcast Thursday night, according to a statement by Worldwide Pants Inc., Letterman's production company.

"This morning, I did something I've never done in my life," Letterman told his audiencet. "I had to go downtown and testify before a grand jury."

Letterman revealed to the studio audience that he has received a package three weeks ago containing a threat to reveal those indiscretions "if Letterman did not pay the individual a large sum of money" -- specified in a later communication as $2 million.

He said that the package contained a letter that said, " I know that you do some terrible terrible things and I can prove that you do these terrible things... and sure enough what was contained in the package was proof that I do terrible, terrible things." The audience, mostly likely waiting for the punchline that never came, laughed nervously along as he went on to describe how he called his attorney and then set up a meeting with his blackmailer.

The plotter told Letterman that he wanted to write a screenplay about him that included sordid details of the talk show host's life.

At a second meeting, Letterman, with the assistance of the Manhattan District Attorney's Office, handed the blackmailer a phony $2 million check. It was then that the extortionist revealed he also planned to write a book about Letterman's life, also revealing details of his past sexual infidelities. "