A Tory MP's chief of staff has been arrested on suspicion of rape following an alleged attack at the Houses of Parliament, the BBC understands.

It is understood the man is Sam Armstrong, a 23-year-old who works for South Thanet MP Craig Mackinlay.

The rape is alleged to have happened in the early hours of Friday and Mr Armstrong was arrested later that day.

The Metropolitan Police confirmed a man had been bailed until mid-January pending further inquiries.

A statement from the office of Mr Mackinlay, a former deputy leader of UKIP, said: "Mr Mackinlay was made aware of an allegation against a staff member and granted permission for the police to access his Westminster office.

"Mr Mackinlay is monitoring the situation and awaits further details from the police and Parliamentary Authorities."

Parliament is also "working closely" with police, the House of Commons said.

"We are aware of an incident on the parliamentary estate which is being investigated by the Metropolitan Police Service," a spokesman said.

"Parliament is working closely with the police on their investigation and we cannot comment further while this is ongoing."