Russell Brand has been accused of exposing himself to a woman then laughing about it on his BBC radio show.
The woman told BBC News it happened in 2008 when she was working in a building in Los Angeles also used by the corporation.
She said she was bending down to look in a medicine cabinet when she realised a man was standing behind her and realised it was Brand.
She said he told her she was “a bit of alright” and then said “I’m gonna f*** you” before exposing himself.
Later that day, she said another member of BBC staff told her Brand was talking about what he did in the studio.
An episode of The Russell Brand Show, broadcast on June 21, includes a segment where Brand’s co-presenter Matt Morgan tells the audience: “It’s been 25 minutes since he showed his willy to a lady” which prompted Brand to burst out laughing and say “Very easy to judge!”.
In a statement, the BBC said it was sorry to hear the allegations and they would be investigated as part of a previously announced review into Brand’s time at the BBC.
Four other women have also accused the 48-year-old of sexual assaults and rape between 2006 and 2013. He has denied the claims, saying his relationships were "always consensual".
The woman, who the BBC has not identified, said: ““I feel ashamed, but more so I wonder had something been done, perhaps there would have been fewer women he would have done horrible things to, which we’re reading about in the papers now.”
The latest allegation comes as it was announced the team set up after Jimmy Savile’s abuse came to light is helping police looking into the rape and sexual assault allegations made against Brand.
Earlier this week, Scotland Yard said it had received a report of an alleged sexual assault in the wake of media allegations about the 48-year-old comedian and actor, which he strongly denies.
On Thursday, the Hydrant Programme – national experts on child sexual abuse inquiries – urged people to report any allegations to investigators.
The Evening Standard approached Mr Brand’s representatives for a comment.
