Maverick Labour MP will be asked for loyalty pledge

Paul Marsden, the rebel Labour MP who has made a stand against the bombing of Afghanistan, will be ordered to give a loyalty pledge by Hilary Armstrong, the Chief Whip.

The Shrewsbury and Atcham MP will be asked in a meeting on Monday to dispel persistent rumours that he is negotiating to join the Liberal Democrats. He will also be warned that he faces disciplinary action for issuing a press release accusing named colleagues of physically and verbally assaulting him.

The carpeting follows a series of alleged confrontations this week between Mr Marsden and Labour whips. He has written to Tony Blair and the Speaker of the Commons, Michael Martin, demanding action to end alleged intimidation.

The Labour Party said other backbenchers had complained about his press release, which was headed "Labour thugs attack MP". It said the action contravened the code of conduct for MPs, which forbids "personal attacks upon colleagues orally or in writing" and bringing the party into disrepute. A spokesman said Ms Armstrong would challenge him on "sustained and substantial" speculation that he is about to join the Liberal Democrats. "Our assumption is that he is not about to do it, but these rumours need to be put to bed, for the sake of his constituents."

The spokesman said the allegations made by Mr Marsden were being investigated by the Chief Whip.

In a letter to Mr Marsden, Ms Armstrong wrote: "My inquiry will not be concerned with your views on the conflict in Afghanistan or on the passage of the Anti-Terrorism, Crime and Security Bill. You are, and always have been, free to express your views and represent your constituents as you see fit. However, all members of the Parliamentary Labour Party give an undertaking to work within the scope of the Code of Conduct.

"I shall be seeking an undertaking from you that you intend to work within the same framework as every other member of the Parliamentary Labour Party." She will report on the meeting to the party's parliamentary committee, which could discipline him. It does not have the power to expel him from the party.

Mr Marsden named five whips when he complained of "bully-boy tactics" in late-night confrontations in the Commons chamber and a Commons bar, as he sat with Liberal Democrat MPs for neighbouring constituencies. He said one put his arm around his throat, another prodded him in the back and several hurled expletives at him. His claims have been fiercely denied by the whips but Liberal Democrat witnesses confirmed the clashes.