Police are investigating a third claim of sexual assault against actor Kevin Spacey, Scotland Yard has confirmed.

A third man has made allegations to police that he was assaulted by Spacey in London in 2005.

"On December 13 we received an allegation that the man sexually assaulted a man (Victim 3) in 2005 in Westminster," a spokesman from London's Metropolitan Police said.

Spacey was artistic director at The Old Vic for 11 years. Credit: PA

Spacey has not been named as the alleged perpetrator but police confirmed it was the man who is being investigated over alleged offences which took place in Lambeth in 2005 and 2008, who has previously been identified as Spacey.

Following the first known allegation against Spacey from actor Anthony Rapp, which was made in October, a number of men and women have reported inappropriate behaviour from the Usual Suspects actor.

The Old Vic theatre in London, where Spacey was artistic director from 2004 to 2015, says it has received 20 complaints against the actor.

American law enforcement have also stated they've opened investigations into Spacey.