Labour MP Eric Joyce is in police custody after being arrested over an alleged late night assault in a House of Commons bar.

The former soldier was arrested by Scotland Yard officers after reports he head-butted Conservative Stuart Andrew shortly before closing time on Wednesday night in the Strangers Bar, Parliament's pub for MPs.

Mr Andrew, MP for Pudsey, who has no visible cuts or bruises, responded to concerns about his welfare on Twitter by writing: "I'm ok."

Labour suspended Mr Joyce from the party pending the results of the police investigation, branding the incident "extremely serious", though he remains MP for Falkirk.

The Metropolitan Police confirmed officers detained a man in his 50s after being called to reports of an incident at a bar within the Palace of Westminster at around 10.50pm. He was taken into custody at a central London police station and remains there.

A Labour Party spokesman said: "This is an extremely serious incident. We have suspended Eric Joyce pending the results of the police investigation."

Speculation about the incident has been rife in Westminster but Commons Speaker John Bercow thwarted any attempt to raise the matter in the chamber by issuing a stern warning at the start of proceedings.

He told MPs: "I have been informed by the Serjeant at Arms that the honourable member for Falkirk has been detained in police custody.

"The matter is being investigated. I take this matter very seriously, as do the House authorities. I would ask that no further reference should be made to these reports in the Chamber today."

Mr Joyce, MP for Falkirk since December 2000, served in the Army Education Corps before pursuing a career in politics. In 2010 he resigned as shadow Northern Ireland minister after pleading guilty to failing to provide a breath test.