Scott Thorson, 54 — whose life with the pianist was turned into film Behind The Candelabra — said he began bedding Jacko in 1982 after he and Liberace split.
He said: “I was introduced to Michael Jackson through Liberace back in 1977 and we had a fantastic relationship.
“When we broke up in 1982, Michael swept me off my feet and said, ‘Hey, I’m breaking away from the Jackson 5. I’m going solo’. This is when the Thriller tour started. Michael swept me off my feet.”
Asked on Aussie radio if they were lovers, Scott replied: “Yes, for a short time.
“It was short term because Michael became very big at the time and his management team thought it best that we didn’t go any further with our relationship.”
He claimed they were wary of his court battle for a £73million payoff from Liberace — who died in 1987 aged 67. The case was eventually settled for just £60,000.
Scott — currently on US probation for identity theft — said he and Jacko stayed pals until the star, 50, died in 2009 from a drugs overdose.
He added: “It was very sad. But it just goes to show what these plastic surgeons can do to you — or any doctor for that matter.
“Michael started his drug addiction because of the plastic surgeons.”