Former Labour MP Eric Joyce is reportedly being held by police after another brawl in parliament, just over a year since he was suspended from the party for a similar incident.
The MP for Falkirk was arrested at the Sports and Social bar in the parliamentary estate after becoming embroiled in an altercation with policemen.
He has now been banned from buying alcohol on the parliamentary estate indefinately by the Commons authorities.
"Police were called shortly before 10.30pm this evening to reports of a disturbance at a bar within the House of Commons," the Metropolitan police said in a statement.
"Officers attended and a man aged in his 50s was arrested in connection with this incident."
The man remains in custody, Scotland Yard said.
Tony Grew of the PoliticsHome website witnessed the scene and said the independent MP was already "agitated" when he entered the bar, which was holding a karaoke night.
Joyce reportedly became involved in an altercation after complaining about being prevented from taking his glass outside to the smoking area. By the time Grew followed him outside the MP was wrestling on the ground with two police officers.
"He appeared to have one of the officers in an armlock, he put his arm around the officer's neck, and the other police officer was on top of him," Grew told ITV.
"There were around at least 40 or 50 parliamentary staff, shocked, watching this melee as it occurred. Bar staff were trying to push people back, telling them to stand back and let the police do their work.
"I can vividly remember a policeman's hat rolling on the ground towards me as I was watching this scene unfold."
Later the journalist saw Joyce on a bench, in handcuffs, being held down by three or four officers, still struggling.
Joyce first resigned from the Labour party after he was arrested for headbutting Tories Stuart Andrew and Ben Maney in another parliament bar in February 2012.
The 52-year-old walked into the Strangers' Bar and complained loudly it was "full of f***ing Tories" before launching into the attack, which also involved Tory councillor Luke Mackenzie and Labour whip Phillip Wilson.
The former soldier was fined £3,000 and ordered to pay £1,400 to each of his victims. He was also given a 12-month community order, banned from entering pubs of licensed premises for three months and received a curfew order from Friday to Sunday.