British police are investigating an allegation of rape at the Houses of Parliament against an aide to a Conservative Party MP, the politician's spokesman said on Tuesday.

London's Metropolitan Police on Monday announced an investigation into the alleged rape which is said to have occurred in the early hours of October 14.

“A 23-year-old man was arrested that same day on suspicion of rape. He has been bailed pending further inquiries to a date in mid-January 2017,” the Metropolitan Police told AFP.

Investigators did not publicly name the victim or the suspect, who was identified by British media as an aide to MP Craig Mackinlay who represents the ruling Conservative Party.

A spokesman for Mackinlay said the politician “was made aware of an allegation against a member of his staff” on Friday morning. Following a request made by the police and parliamentary services he granted full access to his Westminster office. Mr Mackinlay is currently awaiting further information from the police,” they told AFP.

A spokeswoman for the Conservative Party said: “It would be inappropriate to comment while a police investigation is taking place.”

As police enquiries continue, the House of Commons staff were working with the authorities.

“We are aware of an incident on the Parliamentary Estate which is being investigated by the Metropolitan Police Service.

“Parliament is working closely with the police on their investigation and we cannot comment further while this is ongoing,” a spokesperson said.

London's Houses of Parliament, also known as the Palace of Westminster, serve both as the centre of British politics and iconic tourist attractions, famed for the Big Ben clock tower.

Designed by Charles Barry and Augustus Pugin, the Houses of Parliament were completed in 1870 and are now a Unesco World Heritage Site.