According to The Associated Press, the Old Vic theater said Thursday that the 20 alleged incidents took place from 1995 to 2013. Spacey, 58, was artistic director there from 2004 to 2015.
The theater, which said the allegations followed an investigation into Spacey's behavior that began last month, said it "truly apologizes for not creating an environment or culture where people felt able to speak freely," the BBC reported.
The news is the latest in a string of allegations of sexual misconduct against the actor, starting with a claim by "Rent" star Anthony Rapp that Spacey made a sexual advance toward him when Rapp was just 14. Spacey issued a controversial apology on Twitter, claiming he did not remember the incident if it had occurred. He publicly came out as gay in the same statement, sparking criticism that he was trying to tie being gay to predatory behavior.