WWW- TOM Cruise is furious a gay porn actor is investigating his private life.

Friends of the movie star said yesterday author Andrew Morton [pictured] had “sunk to a new low”.

Morton, who collaborated with Princess Diana to produce an account of her troubled life, is paying 58-year-old Paul Baressi to help him with his warts-and-all book about Cruise.

Baressi has starred in 25 gay porn films but now works as a private investigator in LA.

“I am a key source of information regarding several things,” Baressi said.

Baressi claims to have provided Morton with documentation regarding a bizarre episode in which Cruise, 43, was falsely accused of having a homosexual encounter while shooting the film Eyes Wide Shut in the UK.

Yesterday Cruise’s lawyer Bert Fields said the actor would sue Morton and New York-based publishers St Martin’s Press if they used the letter he wrote in response to try to cast aspersions on Cruise’s sexuality.

“I wrote a letter to Mr Morton back in November and said he obviously was entitled to write the book but ‘make sure you check your facts’,” Mr Fields said. “If he tries to use my letter to create the impression that Mr Cruise did have a gay affair, we will certainly sue … because the story is false.

“Mr Cruise is not gay.”

A friend of the actor said: “Morton is scraping the bottom of the barrel. If Baressi is the best Morton can come up with, that just goes to show how low Andrew Morton has sunk.”