LOS ANGELES, USA - The David Letterman extortion affair and sex scandal is proving a late night ratings bonanza for TV network CBS.

Some 5.7 million people tuned in on Monday to hear Letterman apologize to his wife and staff for his on-air revelations last week about his sexual affairs and an alleged blackmail plot.

That was a 36 percent increase over the audience for the "Late Show with David Letterman" on Monday last week, and a 19 percent jump on the 2009-2010 season-to-date average for the talk show of 4.8 million viewers, CBS said on Tuesday.

Show business newspaper Daily Variety noted that Monday's Letterman ratings at 11:30 p.m. were higher than anything struggling NBC had on Monday in prime time, including its returning drama series "Heroes," new medical series "Trauma" and "The Jay Leno Show" at its new 10 p.m. slot which pulled in 4.3 million viewers.

Letterman told his audience on Monday that his wife Regina, with whom he has a 5-year-old son, had been "horribly hurt" by his behavior and that he was trying to patch things up.

On Thursday last week, Letterman stunned Americans when he said he was the target of a US$2 million (S$2.8 million) blackmail attempt, and then admitted having sexual affairs with women on his staff.

One day later a CBS news producer pleaded not guilty in connection with the alleged extortion. He faces up to 15 years in prison if convicted.