Tony Blair has welcomed an announcement that the IRA has destroyed all of its weapons as an "important step" to lasting peace in Northern Ireland.
Mr Blair called on all paramilitaries to decommission arms
Failing to do so for the last decade had been an "impediment", he said, and urged all paramilitaries to follow.
Shadow Northern Ireland Secretary David Lidington said decommissioning was "important" but just part of change.
Liberal Democrat Northern Ireland spokesman Lembit Opik said it was now time for a "normalisation" of politics.
Earlier, General John de Chastelain, the head of the arms decommissioning body, announced that the decommissioning represented "the totality of the IRA's arsenal".
However, unionists are unhappy there has been no photographic evidence.
Mr Blair said: "Successive British governments have sought final and complete decommissioning by the IRA for over 10 years.
"Failure to deliver it had become a major impediment to moving forward the peace process.
"Today it is finally accomplished. And we have made an important step in the transition from conflict to peace in Northern Ireland.
"If the IMC confirm that all other activity has ceased, then that transition, as far as the IRA are concerned, will be complete."
Two churchmen - Catholic priest Father Alex Reid and ex-Methodist president Harold Good - who sat next to General de Chastelain at a press conference, said they had witnessed the decommissioning process.
Mr Lidington said: "Had this happened five and a half years ago, in line with the original timetable set out in the Belfast Agreement, then its value as a means of building trust and confidence among unionists in the political process could have been of decisive importance.
"Decommissioning is important, but it is only one element of what is needed for the republican movement to complete the transition for terrorism to peaceful and democratic politics.
"People in Northern Ireland will now want to see clear evidence that all forms of paramilitary and other criminal activities - including intimidation, shootings, beatings, robberies, smuggling, money-laundering and exiling people from their homes - has ended for good."
Mr Opik said: "I don't need photographs to prove it, and those who claim they are essential are simply holding out against the logic of the situation."
He added: "Reasonable people will be reassured that there will not be a return to the widespread terrorism of the last 30 years."
Mr Opik said there was no excuse for politicians on all sides to resist sensible negotiations - what he called a necessary step towards restarting devolution.