As US TV star David Letterman makes attempts at humoring his way out of his marital woes and work place sex scandal, new details are popping up of the extortion plot that was planned against him.

The latest information is that the host of the Late Show allegedly maintained a sexual relationship with his ex-assistant following her move to live with her boyfriend, who happened to be Letterman’s accused extortionist. The TV host, who likes to poke fun at everything that moves, such as public figures caught with their pants down, has attempted to lighten up the scabrous tale after confessing to having sex with several female employees.

Letterman’s management team has insisted that the sexual affairs predate his marriage to Regina Lasko, his longtime girlfriend and mother of his son, 5 year-old Harry.

Meanwhile, a number of female former assistants have come forward to volunteer information of liaisons with the TV personality, who apparently had a fold-out bed in his Ed Sullivan Theatre office in New York.

Holly Hester, an ex-intern on the Late Show, said she was involved in a year-long affair with Letterman in the 1990s. Hester claimed to have been madly in love with him, adding that she would have married him.

Another former female staff, writer and producer Merrill Markoe, poked fun at her idyll with the star on her blog. She wrote that Letterman had promised her she would be the girl he would ever cheat on.

But the young woman at the centre of this sordid story is 34 year-old Stephanie Birkitt, another former assistant. She had moved in with boyfriend Robert Halderman, a CBS producer. The pair decided to separate in August, and Mr. Halderman allegedly got hold of his ex’s diary which contained details of her affair with Letterman and used it to blackmail the TV host for $US2million ($2.2m).