David Letterman took mistress on vacation with his wife

David Letterman apologizes on his show. Photo: AP

The NY Post has reported that David Letterman brought his younger assistant Stephanie Birkett, with whom he was having an affair, along on a Caribbean vacation with his wife and son.

Letterman's wife, Regina Lasko, apparently believed that Birkett was "an innocent 'friend' and 'coworker' at the time."

Birkett was identified as one of the women Letterman was having affairs with last week after her current boyfriend, CBS Producer Robert "Joe" Halderman, was arrested for blackmailing Letterman.

Halderman's friend, Dr. Bob Arnot, said on ABC's Good Morning America Thursday that Halderman saw Birkett and Letterman "in a very passionate embrace."

Halderman allegedly decided to extort Letterman over revenge and jealousy.

FOXNews.com reported that Lasko was the one who demanded Letterman issue a public apology to her on his show last Monday. Sources said Letterman "wanted the whole thing to blow over. But Regina told him he better make an apology to let everyone know how sorry he was for how much he hurt and humiliated her."

However, Lasko was apparently not happy with the jokes Letterman threw in about his affairs. The source said, "Regina felt like Dave's humorous apology lessened the sincery of it, and she's not happy at all."