Jason Francia, 24, has told Santa Maria court, California, the pop star abused him three times as a young boy, groping him as they played at his Neverland ranch.
Under cross-examination he revealed in his first interview he told detectives Jackson had not molested him.
Defence lawyer Tom Mesereau suggested he had been bullied into making the allegations and asked whether the police had become aggressive.
But Mr Francia said he could not remember details of the interview.
He has already told the court he initially denied it because he did not want people to think he was gay and desperately wanted to forget the incident and put it behind him.
“I was scared,” he said.
Mr Francia, whose mother worked as a maid at Neverland, described how he used to play in Jackson’s “hideout” while his mother cleaned.
He broke down in the witness box on Monday as he recalled how Jackson’s hand had allegedly slid up his shorts and touched his testicles for some two or three minutes.
Mr Francia and his mother, Blanca, received a settlement of more than $2 million from Jackson in 1994.
Blanca Francia took the stand after her son and began to describe how she cleaned Jackson’s so-called “hideout” apartment in Los Angeles.
Mr Francia has claimed she found money Jackson had stuffed in his pockets after the first two alleged acts of molestation.
Michael Jackson denies all the charges he faces.
Meanwhile, it emerged Jackson’s former publicist is to publish a tell-all book detailing the singer’s relationships with several young boys.
Bob Jones, who was fired last year after 30 years with Jackson, promises to reveal intimate details about the embattled pop star’s dealings with a host of young playmates including Macaulay Culkin, Jordy Chandler and Emmanuel Lewis.
Co-writer Stacy Brown told the New York Post’s Page Six column: “Bob confronted Michael a few times about his behaviour with little boys.
“In no uncertain terms, Michael told Bob to mind his own business.”
Michael Jackson: The Man Behind the Mask will allege Jackson has a penchant for playing sick when he does not want to make a scheduled appearance.
Brown claims the star once checked into a hospital and said he had chest pains because he did not want to perform at a concert.
Both Brown and Jones have been subpoenaed to testify at Jackson’s trial.
Their book is expected to hit bookshelves by the end of April.