The Secretary of State for Northern Ireland told a hushed chamber that the Northern Ireland Bill, which tightens the legal "failsafe" intended to guarantee disarmament by the IRA, was the "best chance for peace we have ever had".
But Ms Mowlam, flanked by Tony Blair, faced fierce criticism from David Trimble, the Ulster Unionist leader, and Tories who said the proposals meant democratic parties would be punished for paramilitaries' failure to decommission.
The Bill was to be rushed through all its Commons stages in just one sitting last night despite attacks from Ian Paisley, the Democratic Unionist Party leader, that such short time was insufficient for such an important measure.
Under the legislation, if commitments are breached by either side on decommissioning or on devolving the institutions set up by the Good Friday Agreement, the institutions will be suspended. Northern Ireland would be returned to direct rule with the executive brought to an end.
The precise timetable of decommissioning of paramilitary arms has been left to an independent body headed by General John de Chastelain. Ms Mowlam said he made clear "there will be a process of decommissioning within days of the devolution and there will be, within weeks, the first act of decommissioning".
To Tory shouts of "How long?" Ms Mowlam said: "Any suggestion in the past has been a token gesture. Why this, I believe, is the best option we have ever had to make real peace in Northern Ireland, is [that] it will be a timetable for complete decommissioning by May 2000. That, I believe, is worth taking a risk and it is, I accept, partially a risk. It is partially a risk because what it does is say that after d'Hondt on Thursday, after devolution on Saturday, it will be a matter of days before the process starts and weeks before actual decommissioning starts.
"Now is that too long to wait to see if this process can work? We will know who is serious. We will know which side isn't going to fulfil their agreements within weeks. I think that is worth doing to see if we can get real decommissioning."
But Roy Beggs, the Ulster Unionist MP for Antrim East, said the impression given was that she and others had been prepared to turn a complete blind eye to murder, to beatings and mutilations and to the number of families intimidated and driven out of the country.
"What do you say to those who have formed that impression? How can you give us any confidence that serious terrorist activity by terrorist organisations will not be ignored in the future?" Andrew Mackay, the Shadow Northern Ireland Secretary, demanded that Sinn Fein should be automatically excluded from the executive if the IRA failed to decommission.
"I have never known a situation before where everybody is punished equally. Those who have done no wrong and have fulfilled their obligations are being punished in exactly the same way as those who fail to fulfil their obligations by not decommissioning. That cannot be fair and equitable."
The Opposition also wanted a halt to prisoner releases if any paramilitary group failed to decommission - to give an assurance to republicans that there would be loyalist decommissioning as well.
"These are true failsafes that avoid a fudge," said Mr Mackay. The only way to get round the lack of trust on both sides was to provide "copper bottomed guarantees in law".
Mr Trimble said the Prime Minister knew his party was "reluctant" to take part in an executive with Sinn Fein in advance of decommissioning. "Our reluctance will be portrayed by some as an unwillingness to share in an administration with Catholics or nationalists. This is untrue."
He said his party did not even have an "absolute objection" to sitting down with past terrorists.
"Our problem isn't with former terrorists. It's about taking an existing and active terrorist organisation into government. For that is what the Government now proposes." He condemned the so-called "failsafes" as "flawed and unfair".
They were unfair because if Sinn Fein broke their obligations then everyone in the executive was ejected from office. "The innocent are punished along with the guilty and the democrats are treated as if they were indistinguishable from the terrorists.
"The fair response is that the offending party should be removed. If that was in the Bill it would go a long way to making it acceptable. But it is not."Reuse content