Conservative politician Mark Pritchard has been arrested on suspicion of rape.
The Tory MP for The Wrekin in Shropshire has since been released on bail pending further inquiries.
News of his arrest was given to the House of Commons speaker John Bercow in a letter from the Metropolitan Police, according to Votes and Proceedings.
A Met Police spokesperson said: "We can confirm that a 48-year-old man voluntarily attended a north London police station on Tuesday 2 December."
The letter sent to the Commons said: "I write to inform you that on 2nd December 2014, Mark Pritchard MP was arrested at 6.14pm at Holborn Police Station in London by MPS officers.
"Mr Pritchard was questioned by police and released on bail later the same evening at 10.16pm. The matter is subject to further investigation and is sub judice at the present time."
A Conservative spokesperson added: "This is a police matter. It would be inappropriate to comment while an investigation is taking place."
The MP has been bailed until early January 2015. No further details of the alleged offence were immediately available.