The UK Parliament has begun rushing through measures that are likely to result in the suspension of devolution for Northern Ireland by the end of the week.

Political institutions in the province could be frozen after just two months due to the political crisis sparked by the failure of the IRA to begin decommissioning.

Putting the Northern Ireland Bill before MPs, Northern Ireland Secretary Peter Mandelson said direct rule from Westminster would be re-imposed unless there was "substantive progress" towards decommissioning.

MPs passed its Commons stages on Tuesday night, and is expected to clear the House of Lords by Thursday and gain Royal Assent on Friday.

Sinn Fein MP Martin McGuinness, who is unable to sit in the House after refusing to pledge loyalty to the Queen, sat in the public gallery, just above the heads of Ulster Unionists, as Mr Mandelson delivered his opening speech.

To give the peace process the chance to find a way through its latest impasse Mr Mandelson said it would be necessary to "create a pause in the operation of Northern Ireland's political institutions".

Explaining the decision not to publish General John de Chastelain's report on decommissioning, Mr Mandelson said both the British and Irish governments had agreed that "no useful purpose would be served" by doing so.

His Tory shadow Andrew Mackay said failing to make the report available, "if not an abuse, is riding roughshod over the House".

But he pledged his party to support the bill, saying the lack of decommissioning left little choice.

Mr Mandelson, saying decommissioning was vital to the peace process, said the choice facing MPs was between suspending the Northern Ireland's political institutions or seeing them collapse.

"The choice is between pause or bust," he said.

Unionists 'jumped first'

Ulster Unionist leader and Northern Ireland's first minister David Trimble told MPs he was disappointed that after his party had "jumped first" by entering into government with Sinn Fein, the IRA had not reciprocated by handing in their arms.

Mr Trimble said: "If we took the initiative there was an understanding that we could only sustain that for a limited period."

But Seamus Mallon spoke out against the suspension of Northern Ireland's executive and assembly for the nationalist SDLP.

He warned MPs: "It seems abundantly clear that the chances of actually achieving decommissioning will be greatly reduced if the institutions are not there and functioning."

'Confidence measures'

Lembit Opik, for the Liberal Democrats, told MPs the legislation to suspend the assembly was "probably" the right course of action, but said the government "must not ride roughshod over the concerns that have been expressed in those (nationalist) communities".

He said: "I would ask Mr Mandelson and his government to very seriously consider what confidence measures they can take if indeed they decide to invoke this bill."

Former Prime Minister John Major suggested the leaders of Sinn Fein might want decommissioning to begin but did not yet have the support of their movement.

Later, opening the third reading debate, Mr Mandelson rounded on anti-agreement unionists and their "rejectionist mentality", saying they did not speak for the majority of the people in Northern Ireland.

He said most MPs wanted the peace process to succeed "rather than playing some ridiculous, destructive blame game".

The bill now goes before the House of Lords on Wednesday.