The British government tonight faced a barrage of protests over moves to deal with Northern Ireland's "on-the-run" terrorist fugitives.
Both the Prime Minister and Northern Ireland Secretary Peter Hain struggled to defend the Northern Ireland (Offences) Bill.
A Tory bid to block its Commons second reading because it "creates an amnesty for terrorist fugitives" was rejected by 313 to 258, a majority of 55.
Second reading was then approved by 310 to 262, a margin of 48.
Mr Blair said he understood the "pain and anguish" the legislation would cause but insisted it was vital for the peace process.
"If it (the peace process) does succeed - and we have come a long way in eight years - it is sometimes because we do things that are uncomfortable and difficult but nonetheless necessary.
"It is called, I'm afraid, making difficult political decisions," he told Charles Kennedy at question time after the Liberal Democrat leader raised concerns about the Bill.
Under the measure, those wanted by police for offences committed before the Belfast Agreement was signed in 1998 will have their slate effectively wiped clean.
Mr Hain insisted the move was necessary to bring closure to the IRA's "awful and murderous" campaign and ensure there were "no victims of the IRA in future".
But he looked uncomfortable as he faced a series of angry interventions from MPs on all sides of the House opposing the Bill
Democratic Unionist Iris Robinson warned the legislation would not bring closure but "more pain" for victims.
The Rev William McCrea
described seeing his two young cousins after they had been blown up by the IRA.
"I'm asking you to tell me am I to bury justice to appease murderers of the IRA?" he asked, his voice breaking with emotion.
Labour former minister Frank Field contrasted the Government's treatment of white Protestant and Catholic terrorists with that of black Muslim ones and accused ministers of sending "conflicting messages".
Tory former leader Iain Duncan Smith described the Bill as "grubby and reprehensible" and as "one step too far".
At one point Speaker Michael Martin had to intervene, warning he would suspend the sitting if angry shouting from backbenchers continued.
Mr Hain said many would find the legislation "very hard to bear" but now was the appropriate time to deal with the issue after the IRA's "historic" renunciation of violence.
He insisted there would be "closure" for the victims and denied the Bill amounted to an amnesty.
If on-the-runs were convicted under the legislation, they would be released on licence and could be re-arrested if they broke the terms of that licence.
"The choice is stark: either many of these people continue to run free, never having to account for their crimes, or we put them through these special procedures to face the possibility of conviction," he said.
MPs from all sides condemned the Bill for not requiring the alleged perpetrators of crimes to appear before the court.
DUP leader the Rev Ian Paisley said the Bill was "an attack on the most basic elementary elements of justice" and should be kicked out.
"Yet again it demonstrates that the Government is prepared to enthrone expediency and dethrone principle.
"I never thought I would be a Member of the British House of Commons discussing such a Bill from any government."
He said that at the same time as ministers were accusing MPs who voted against 90-day detention without trial of being "soft" on terror, the Government was putting forward "a complete sell out of the British justice system".
"Tonight we are setting up two systems of justice: one that has on it the light of democracy and liberty and law and the other that is a court that has upon it the finger marks of the IRA."
PA