MR Tony Blair joined Mr John Major yesterday in confronting Sinn Fein with "a moment of truth" in the aftermath of the Manchester bombing.
Asserting the Westminster consensus, the Labour leader told the prime minister "the US and others abroad have perhaps been given a telling lesson in the realities of the IRA".
And Mr Blair declared: "Is this not a moment of truth for Sinn Fein? Doesn't it show the wisdom of demanding a ceasefire before they participate in any talks and doesn't the responsibility now lie squarely upon them if they are to play any part at all in the future progress of peace?"
The prime minister readily agreed: "The time has come for Sinn Fein to make up its mind. Either it's going to be a democratic organisation, taking part iris democratic politics or it's going to stay side by side as the reverse coin of the IRA, with intermingled membership, in which case it has no part, in democratic politics' whatever.
Mr Major stressed that for Sinn Fein to enter talks the IRA must call an "unequivocal ceasefire immediately and show it is credible, it is lasting and is not just a tactical device".
Mr Major condemned Saturday's bombing as "a callous and inhuman act". It was a miracle, he told MPs, that many more people had not been injured or indeed killed. And he continued angrily: "What is so startling is the total indifference of the people who left that bomb to the fact that well could have happened to many people who had no connection whatsoever with the disputes that are in Ireland, or the disputes the IRA may have with the British government."
Endorsing Mr Major's call for an end to "the measly nonsense: we have had from them [the IRA and Sinn Fein] in recent years", Mr Blair said: "Wouldn't you also agree that there has been progress in Northern Ireland. The British and Irish governments are agreed on the way forward.
"All nationalist parties in the Irish Republic and Northern Ireland, apart from Sinn Fein, are agreed on peaceful means to achieve their ends. The US and others abroad have perhaps been given a telling lesson in the realities of the IRA. Isn't the only course now open to Sinn Fein to ensure the IRA ceases its violence or if it cannot or won't then this peace process should proceed with the democratic parties, an agreement should be reached and put to a ballot of the people."
Mr Major replied it was "entirely right that these [multi party] talks should continue". He said: "We have no intention of allowing the search for a political settlement to be derailed by the activities of the IRA and the activities of Sinn Fein. I hope that all the constitutional parties in Northern Ireland will continue, to demonstrate the leadership and courage necessary to make rapid progress and show the IRA that they cannot stop the process by bombs in Manchester, London or anywhere else."
Mr Major continued: "Clearly, if they wish to have any future interest in this process they will need to declare an unequivocal ceasefire. They will need to declare it immediately and they will also have to show that ceasefire is credible, is lasting and is not just a tactical device to enable them to enter the talks until such time as it is convenient for them to leave."