A letter obtained by Allhiphop.com, by lawyer Lisa M. Buckley of Pryor Cashman reads: "Be advised that the Screen Shot, as well as the Tape from which the Screen Shot was taken, were illegally obtained and believed to have been stolen from Mr. West's computer.

"You're posting, advertising, marketing, displaying and otherwise disseminating the stolen Screen Shot and/or other materials on the Tape constitute actionable violations of Mr. West's rights of privacy and publicity."

The lawyers are also seeking information as to who is attempting to sell the tape, which is in demand, with Sex.com offering $1 million to the anonymous person for the tape.

Steve Hirsch of pornography company Vivid Video - who released Kanye's girlfriend Kim Kardashian's sex tape which saw her star with rapper Jay J - said Kanye's sex video could be worth millions of dollars.

He said: "It depends on the quality of the tape, the length, the lighting, the sex.

"But something like this could go for a couple of million dollars. I don't think there has ever been a sex tape with a star of this magnitude. [Motley Crue drummer and ex-husband of Pamela Anderson] Tommy Lee was big, but this is a different world and Kanye is a special guy. He's everywhere."