U.S. Tv icon Johnny Carson had a Mafia contract put on him after drunkenly chatting up a gangster's mistress.

A new memoir by Carson's personal legal adviser, Henry Bushkin, alleges the Tonight Show host had been drinking heavily in Frank Sinatra's favourite New York bar, Jilly's Saloon, when he decided to hit on the wrong woman.

Bushkin writes in his new book, titled simply Johnny Carson, "An attractive brunette caught Carson's eye, and he was doing his considerable best to convince her to leave with him."

When the woman's boyfriend arrived, Carson discovered he was a main main in the mob - and he promptly threw Carson down a flight of stairs before the bar's owner stepped in to break it up.

Bushkin claims the gangster ordered a hit on Carson as a result of the incident, and the Tv personality was forced to hide out at his New York home and miss out on filming three shows until a middleman cut a deal with mob boss Joseph Colombo and Carson was let off the hook.