Labour MP Eric Joyce was taken away from the Strangers Bar in the Commons and arrested by police on Wednesday night, after headbutting a Tory MP and attacking several other Conservatives.
Joyce, who represents Falkirk for Labour, is said to have headbutted the Tory MP for Pudsey Stuart Andrew in the bar, which is reserved for MPs and their guests.
Joyce is thought to have attacked three other Conservatives and one Labour MP during the incident, which happened at around 11pm, three hours after the Commons had risen for the evening.
The bar had been busy, with the Speaker of the House of Commons in Canada, Andrew Scheer, among the guests invited there by MPs.
The Commons had seen a series of rowdy debates on the NHS earlier in the day, with a fiery exchange at PMQs between David Cameron and Ed Miliband. This was followed by a long and rancourous debate over whether Andrew Lansley should publish the NHS Risk Register.
The PoliticsHome website quotes sources as saying Joyce had complained that the bar was "full of Tories". Strangers Bar sees MPs from all parties drinking there every night that the Commons sits.
A Scotland Yard spokesman told the Press Association "We were called at approximately 10.50pm (on Wednesday) to reports of a disturbance at a bar within the House of Commons. A man aged in his 50s was arrested by officers on suspicion of assault. He remains in custody in a central London police station. Inquiries are continuing."
Following the incident Labour announced Joyce had been suspended from the party until the completion of the police investigation into the alleged assault.
Joyce, the MP for Falkirk since December 2000, served in the Army Education Corps before pursuing a career in politics.
From 2003 Mr Joyce served as a Parliamentary Private Secretary (PPS) to a number of government ministers.
Joyce quit as the PPS to Bob Ainsworth in 2009 due to his concerns over the war in Afghanistan. Prior to that he had been a parliamentary aide to John Hutton, including the period when he was defence secretary, Mike O'Brien and Margaret Hodge.
Andrew, who is said to be the victim of the assault, took to Twitter on Thursday morning to reassure people he was ok.
The Strangers Bar has seen more than its fair share of controversy so far this year, after Labour MP Kate Green complained about the allegedly "sexist" beer sold there. One of the guest ales in January was called "Top Totty", and after complaints from Green it was withdrawn and replaced with another guest ale, called "Kangaroo Court".
It is also not the first time a MP has been involved in a fight in a House of Commons bar. Last year Labour's Paul Farrelly was involved in a brawl in the Sports and Social bar on the parliamentary estate.
Farrelly said he was acting in self defence after being confronted with a man who "took a swing" at him.