Reacting to the allegations, Spacey posted a note on Twitter saying, "I honestly do not remember the encounter, it would have been over 30 years ago".
Ari Behn, who was married to Princess Märtha Louise of Norway before their divorce past year, told Norwegian radio station P4 that Spacey proposed the pair go outside.
"We had a nice conversation, he was sat next to me", Behn told Norwegian radio station P4. "After five minutes, he says, 'Hey, let's go out and have a cigarette, ' and then he touched me right on the (genitals) under the table". I've been very gratified by the response I've gotten from so many people. Stunned, Behn said he replied, "Eh, maybe later?"
"I got more than I bargained for", Behn quipped, laughing about the incident, before adding, "I had black hair back then and was 10 years younger so was right up his alley".
His wife, 46, is the daughter of King Harald V and fourth in line to the throne.More news: Israel strikes Gaza after rocket fire
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Kevin Spacey has been accused of groping a former Norwegian royal during a 2007 Nobel Peace Prize concert.
Ari divorced Princess Märtha Louise of Norway previous year after marrying in 2002.
It comes after Buzzfeed first exposed sexual assault claims against Spacey in an interview with actor Anthony Rapp, who accused the actor of forcing himself on him when he was only 14 years old.
Spacey's publicist cut ties with the actor on Thursday and it was not known who now represents him, while Netflix severed ties with Spacey, saying it will not be involved in any production of House of Cards if the actor continues to appear in the show. But Spacey also said he couldn't remember the alleged encounter. One ex-employee alleges the actor sexually assaulted him. This does not include 20 anonymous complaints made against him for alleged misconduct at the Old Vic Theatre in London where Spacey was artistic director 2004-2015.