Home Alone star Macaulay Culkin came to Michael Jackson's defense on Wednesday with a declaration that the pop star never molested him and that the charges against his friend were "ridiculous."

Culkin, who has been portrayed by prosecutors as a past Jackson victim, said he was stunned to learn that his name had been invoked at the trial and criticized authorities for failing to contact him - although he later acknowledged that his lawyers had stood in the way.

The 24-year-old former child star's testimony came before jurors watched never-before-seen outtakes from a damaging 2003 TV documentary about Jackson.

In the outtakes a British journalist is shown goading Jackson into discussing his lonely childhood, love for children and hurt over constant "lies" about him in the media.

The almost three-hour videotape moved the 46-year-old pop star's mother to tears as she sat in the courtroom. At one point Jackson appeared upset and dabbed his eyes with a tissue, prompting his lead attorney, Tom Mesereau, to console him.

Dressed in a black pin-striped suit and open-collared white shirt, Culkin appeared at ease on the witness stand as he described Jackson as a close friend and one of the few people who could truly understand his life as a child star.

Culkin's testimony provided a boost to defense lawyers, who are fighting not only the current charges but claims by prosecutors that the entertainer has been molesting or grooming young boys for abuse since the 1990s.

"Did Mr Jackson ever molest you?" Mesereau asked Culkin shortly after he took the stand. "Never," the actor replied.

"Did he improperly touch you?"

"Absolutely not."

"Did he ever touch you in a sexual way?"

"No."

Asked what he thought of the charges against Jackson, Culkin said, "I think they're completely ridiculous."

The actor conceded spending many nights in bed with Jackson at his Neverland Ranch as an adolescent but insisted it was never planned.

"I fell asleep basically everywhere on that ranch. I would basically flop down anywhere," he said.

Culkin said he learned prosecutors had painted him as one of Jackson's victims after "somebody called me up and said 'you should probably check out CNN because they are talking about you.'

"I couldn't believe people were saying these things and people were thinking these things about me," he said. "Nobody approached me or even asked me if the allegations were true... Even if they assumed they were true I would think they could ask me."

On cross-examination Culkin said he was unaware that his publicists and lawyers had prevented authorities from speaking to him, but ultimately conceded his attorney had sent a letter to prosecutors several weeks earlier blocking an interview.

Deputy District Attorney Ron Zonen also pressed Culkin about his sleeping arrangements when he visited Jackson at Neverland. "So when you say you weren't molested your answer more accurately is that you were never molested while you were awake?" Zonen asked.

"As far as I know, he never molested me," Culkin said, adding that it was "unlikely" that Jackson could have abused him while he slept.

Culkin said he had met the boy who accused Jackson of molestation in 1993 and spoke to the entertainer at the time.

"Michael called me a couple weeks before the allegations hit the press and let me know they were not true and don't worry about it and (said) 'I just need you to be my friend right now,'" Culkin said."

Jackson, who has pleaded innocent, is charged with molesting a 13-year-old at Neverland, furnishing the boy with alcohol in order to abuse him and conspiring to commit child abduction, false imprisonment and extortion.