A man has been arrested on suspicion of rape at the Houses of Parliament.
The 23-year-old man, believed to be an aide to Conservative MP, was arrested and has been released on bail.
Police refused to confirm the suspect's name, but said he was not a Member of Parliament.
It has been reported that the aide took a woman to an MP's office in parliament after drinking in a bar in the Palace of Westminster until the early hours of Friday morning.
The Metropolitian Police said in a statement: "Detectives from the Sexual Offences, Exploitation and Child Abuse Command are investigating an allegation of rape at the Houses of Parliament in the early hours of Friday, 14 October.
"A 23-year-old man was arrested that same day on suspicion of rape. He has been bailed pending further inquiries until a date in mid-January 2017. Inquiries continue."
The Commons Serjeant at Arms office, which oversees parliamentary security, said that it was aware of the allegation. “We are working closely with the Metropolitan Police on the matter but cannot comment further at this time.”