Clare Short will be given a formal warning about her future conduct and told she may lose the Labour whip if she maintains her scathing public criticism of Tony Blair.
The former secretary of state for international development will be asked by Hilary Armstrong, the Government's chief whip, to explain her actions since she made her claim that Britain spied on Kofi Annan, the secretary general of the United Nations, before the Iraq war.
Ms Armstrong said that she had been sent more complaints about Ms Short than about George Galloway, expelled by Labour after describing Mr Blair and President George Bush as "wolves" over Iraq.
Strong pressure for formal disciplinary action emerged at the weekly meeting of Labour MPs yesterday. Kevin Barron, among eight MPs to raise the subject of Ms Short's behaviour, said she should be "kicked out of the party". She did not attend the meeting and no one spoke in her defence.
Later Mr Blair discussed Ms Short's future with the Parliamentary Committee, where backbench leaders raise their concerns with ministers. The Parliamentary Labour Party's (PLP) options include issuing a "yellow card" warning about her conduct; a formal reprimand and suspending or withdrawing the whip.
A warning is most likely because the Prime Minister believes a tougher response would provoke another tirade from Ms Short and could turn her into a martyr. One Labour MP said last night: "We want her to get the message that people are fed up with her outbursts and want her to pipe down."
The "serial rebels" will be reminded of the PLP code of conduct on loyalty they signed when they became candidates.