Michael Jackson is lashing out at a former lover of Liberace’s who claims to have had an affair with Jacko. Scott Thorson, 45, says he twice had romps with the Gloved One shortly before splitting with Liberace in the early ’80s.

Jackson’s attorney Steve Cochran tells us Thorson’s story is “false trash.”

But The National Enquirer, where Thorson makes his claim, reports that he passed a polygraph test and is ready to testify in the singer’s child-molestation case about his relationship with Jackson.

Thorson believes he could prove useful to prosecutors if Jackson’s lawyers assert that their client is thoroughly heterosexual and thus would have no interest in boys.

Thorson says that after meeting Jackson in 1979 in Vegas, the two had their first sexual encounter in a London apartment. Thorson, a former model, says he was trying on some new clothes when Jackson motioned him over to the bed where the singer was lounging.

He contends that they had another tryst the following day after a dinner party.

“[Michael] felt comfortable enough to make the first move on me, and I didn’t resist,” says Thorson. “Michael begged me to leave Liberace. I had to say no.”

Thorson admits in The Enquirer that Liberace evicted him from their L.A. home in 1982 after Thorson became addicted to painkillers and other drugs. Thorson later sued Liberace for palimony.

Thorson claims he saw Jackson off and on over the next few years. Twice, he claims, he saw gay-porn mags on Jackson’s nightstand – once with pictures that “looked like young boys.”

Cochran reacted angrily to Thorson’s allegations, saying: “We reserve our right to seek the appropriate remedies” against “any person who makes this claim.”