Hollywood actor Kevin Spacey on Friday spent a second day in the witness box at a London court, denying sexual assault charges and claiming the prosecution case against him was weak.

The two-time Oscar winner, 63, is on trial accused of sexually assaulting four men dating back more than 20 years, including when he was artistic director at London's Old Vic theatre.

The prosecution has claimed he was a "sexual bully" who revelled in making others feel uncomfortable, including by aggressively grabbing men's crotches.

Spacey began giving evidence at Southwark Crown Court in south London on Thursday, calling himself a "big flirt" but denying any aggressive behaviour.

On Friday, he was questioned about one man who alleged that he drugged him and performed a sex act on him while he was asleep at his London flat.

The "American Beauty" and "The Usual Suspects" actor said the pair were "consensually together in a romantic situation", rejecting claims that the alleged victim was asleep when he was assaulted.

Lawyer Christine Agnew told him: "Well, that is the prosecution case."

Spacey replied: "And it's a weak one."

The defence case is that the complainants, who cannot be named as they have anonymity for life under English law, have exaggerated or fabricated their claims.

Spacey described himself as an "affectionate person", saying he had "consensual interactions" with two of the complainants, but accepted he "definitely misread" signs from one other.

His alleged victims "did not let me know" if they went further with him than they intended, he told the court, suggesting they may have regretted it later.

One, who alleged that Spacey grabbed him in the crotch "like a cobra", may have been motivated by "money, money and then money", he suggested.

Spacey denies 12 charges concerning four men, including sexual assault and indecent assault, which are alleged to have occurred between 2001 and 2013.

On Thursday, he told the court his world "exploded" when he was first accused of sexual assault by US actor Anthony Rapp in the United States. 

"There was a rush to judgement and before the first question was asked or answered I lost my job, I lost my reputation, I lost everything in a matter of days," he said.

Rapp's allegations were found not proven last year.

phz/har/imm