Lawyers for Michael Jackson's estate have slammed a new lawsuit filed in Los Angeles claiming that the late King of Pop, who died in 2009, was a "monster" and child molester.

Australian choreographer Wade Robson has filed a claim alleging "childhood sexual abuse," despite testifying at a 2005 molestation trial that the star never touched him, the Los Angeles Times reported.

Lawyers for Robson, who stayed at the singer's Neverland Ranch as a teenager, filed the lawsuit on May 1 asking an LA judge to let him make a late claim as creditor in Jackson's estate, it said.

"Michael Jackson was a monster and in their hearts every normal person knows it," Robson lawyer Henry Gradstein told AFP in a statement claiming Robson had a breakdown last year.

"He collapsed under the stress and sexual trauma of what had happened to him for seven years as a child. He lived with the brainwashing by a sexual predator until the burden of it all crushed him."

Jackson, dogged for years by child molestation charges, was acquitted after a high-profile trial in 2005. But his career never recovered, and he died in 2009 while rehearsing for a doomed comeback tour.

Gradstein cited Jackson as having told the young Robson: "If anyone ever finds out about what we did, we will go to jail for the rest of our lives" and "our lives will be ruined forever."

"This kind of intimidation of a child by a sexual predator is tragically characteristic and effective, keeping them quiet about the abuse -- often for a lifetime," said Gradstein.

Howard Weitzman, a lawyer for Jackson's estate, called Robson's claim "outrageous and pathetic.

"This is a young man who has testified at least twice under oath over the past 20 years and said in numerous interviews that Michael Jackson never did anything inappropriate to him or with him," Weitzman added.

"Now, nearly four years after Michael has passed, this sad and less than credible claim has been made. We are confident that the court will see this for what it is."

Robson's lawyer said the lawsuit was filed "under seal" -- meaning details are not revealed.

"The irony here is that we were the ones who filed under seal and still tried to keep it secret. Amidst all the accusations of a financial motive, no amount of damages is even listed in our papers," he said.

"There are significant legal issues involved in this case that have the potential to impact lives beyond just our client. But the Jackson money machine, in which everyone is indeed financially motivated, is at it once again to keep the truth from coming out. This time, it won't work."

Jackson's mother Katherine is currently suing AEG Live, the promoters of his would-be tour, for negligently hiring doctor Conrad Murray, convicted over the star's death from an overdose of the anesthetic propofol.

The 82-year-old Jackson family matriarch has been in court most days since the wrongful death trial, expected to last at least three months, started last week.