The son of actor Richard Dreyfuss has accused Kevin Spacey of sexual misconduct, alleging that the House of Cards star molested him while his father was in the same room.

Harry Dreyfuss, who was 18 at the time of the incident, made the claims in an essay published by Buzzfeed. In it he described Spacey as a “sexual predator”, who felt “safe” to abuse him, knowing that he “wouldn’t say a word”.

The claims contribute to a growing sexual abuse scandal against Spacey, who has been dropped by House of Cards producers Netflix and is currently the subject of an investigation by police in London.

Dreyfuss claims that the alleged encounter happened in London in 2008 while his father was rehearsing for the play Complicit, which was being directed by Spacey during his tenure as artistic director of the Old Vic theatre.

“It happened one night when the three of us were alone in Kevin’s apartment rehearsing my father’s lines. My father didn’t see, and I didn’t tell him about the incident for many years,” he wrote.

Dreyfuss said that, during the rehearsal, Spacey repeatedly placed his hand on his thigh. He said that his father was unaware of the incident, as he was “deeply focused on his script”. Dreyfuss claims that when he moved to a different seat, Spacey followed him and continued to hold his thigh, before groping his crotch.

Dreyfuss added that he did not alert his father to the alleged incident as he feared that it might start a feud between his father and Spacey. “I didn’t want the play to be threatened,” he said.

“It just never occurred to me that Kevin would be interested in me in the first place. He was an adult man, a hero of mine, my dad’s boss, none of which were categories on my radar for sexual interactions. Besides, I thought, surely he can’t be coming on to me like this right in front of my dad,” he added.

Dreyfuss said he had sought to downplay the alleged incident in the nine years since it occurred by “telling people the story at parties for laughs”. He said that he finally felt emboldened to speak publicly after hearing the claims against Harvey Weinstein. “I came to see how important it is to add my voice to the people who are demanding a better world. A world in which powerful men are no longer allowed to feel safe to do this, or far worse,” he wrote.

In a statement to Buzzfeed, Spacey’s lawyer Bryan Freedman said that the actor “absolutely denies the allegations” made by Dreyfuss.

Richard Dreyfuss, who Harry says was first told of the incident four or five years after it happened, tweeted that he was “incredibly proud” of his son for coming forward.

In the past fortnight, Spacey has been accused of sexual assault and harassment by at least 10 individuals. In an article published by Buzzfeed on Friday, the actor was accused of sexual abuse by three men. Other men to have accused Spacey of assault include the actor Anthony Rapp and multiple crew members on the Netflix drama House of Cards.

Spacey responded to Rapp in a statement last week, in which said that he did not remember the incident but if it did happen it was likely due to “deeply inappropriate drunken behaviour” for which he apologised. He has not yet responded to any of the other allegations, aside from Dreyfuss’s. A representative for the actor said last week that he was “taking the time necessary to seek evaluation and treatment”.

On Friday Netflix announced that it would no longer work with Spacey on House of Cards and had cancelled the release of a biopic of writer Gore Vidal, which Spacey had produced and starred in. Spacey’s publicist has also announced that she had severed ties with the actor.

Meanwhile, officers in Scotland Yard’s child abuse and sexual offences team have confirmed that they are currently investigating a 2008 allegation of sexual assault believe to have been made against Spacey. Police did not identify the actor by name but said that it was looking into a claim that a “a man assaulted another man in 2008 in Lambeth”.

• This article was amended on 8 November 2017 to clarify that Spacey had responded to both Rapp and Dreyfuss.