Scotland Yard confirmed officers from the Child Abuse and Sexual Offences Command are investigating the complaint.
Scotland Yard also said that the allegation was made on November 17, one day after the Old Vic - where Spacey served from 2004-2013 - revealed that it had received 20 complaints of inappropriate behavior by its former artistic director.
The Metropolitan Police force said it had received a complaint "of sexual assaults against a man" in 2005 in the London borough of Lambeth.
Spacey worked as the Old Vic's artistic director from 2004 to 2014.
"On Friday, 17 November, a further allegation was made about the same man".
The Met were already investigating an allegation of assault regarding Spacey against a different man in the same area in 2008.
George Clooney returning to TV in Catch-22 adaptation
The six-part series, based on Joseph Heller's novel, will hail from Paramount Television and Anonymous Content . The package - co-written by Luke Davies ( Lion ) and David Michod ( War Machine ) will be shopped in December.
DOJ investigating Harvard's admission policies
Bhargava recently held fellowships at the Harvard Kennedy School, but she said she is not now affiliated with the school. A spokeswoman for Harvard University said the school would have a response later Tuesday.
Cavazos alleged that Spacey approached him in "unpleasant encounters" which he said he would have termed "harassment" if he were a woman.
Current artistic director Matthew Warchus said: "These allegations have been a shock and a disturbing surprise to many of us".
"This clearly unacceptable and The Old Vic truly apologises for not creating an environment or culture where people felt able to speak freely".
Police would not confirm the identity of the alleged assailant, who was named as Spacey by the Press Association.
This allegation was brought to the attention of police last Friday.
Back-to-work bill passes
NDP education critic Peggy Sattler said students should be given a full tuition refund for the semester. Full-time students will also receive up to $500 to cover costs incurred during the strike.
This time for walking away from skirmish
Kuzma, who also had 10 rebounds, set a new career high in points for the second straight game with a dynamite second half. Ball's teammates ended up in a skirmish along the sideline near midcourt in a game against the Suns .
Confirmed for Week 12 start
The Denver Broncos have made a decision to start Paxton Lynch at quarterback in Week 12, a source told ESPN's Dan Graziano. Joseph had said earlier this month it "wouldn't be fair" to play Lynch when Lynch had just returned to the practice field.
Jawan killed, 2 injured in encounter in north Kashmir
The security forces cordoned off Magam area in Handwara after receiving specific information about the presence of the militants. The terrorists, who were hiding in a house, were asked to surrender but they kept on firing on search parties.
Mugabe ignores deadline to quit, ruling party calls meeting
If the committee recommends impeachment, the president can then be removed if both houses back it with two-thirds majorities. He also says the war veterans' association is going to court to argue that Mugabe is "derelict of his executive duty".
Years later, Manushi Chillar from India becomes Miss World
After winning a position among the top 5 contestants, Manushi was asked which profession deserved the biggest salary and why. In reply to this tricky question, she replied even more beautifully, she said, "I think a mother is of the highest respect".
Dogs may help lonely people walk off heart disease
The world's population can be divided into three groups: people who have a dog, people who want to get a dog and bad people. The researchers can't provide proof dog ownership actually causes a decrease in risk for cardiovascular disease .