THE SDLP leader, Mr John Hume, called for an all Ireland referendum, asking the people to say if they totally disapproved of violence and if they wanted all parties to start dialogue. Neither the IRA nor anyone else could ignore the result of such a referendum.
Telling the House of Commons he "utterly condemned the terrible atrocity", he said Irish people North and South had shown, "their massive will for peace".
"I think that one of the best ways forward now is to let the people speak and let them speak very clearly. Because if they do, neither the IRA or anybody else will be able to ignore them.
And how do I ask you to let them speak: have a referendum in Northern Ireland before the end of this month and ask John Bruton to do the same.
"And put two questions. One, do you totally and absolutely and unequivocally disapprove of violence for any purpose whatsoever on this island? And number two: do you want to see all parties brought to the table to begin the process of dialogue to create lasting stability?"
The deputy leader of the Ulster Unionist Party, Mr John Taylor, said: "This is a very bad day for Northern Ireland, for Great Britain, and for the Republic of Ireland, and we appreciate their united front."
The "inevitability" of another terrorist attack had been increasing because Sinn Fein had been "totally isolating itself", Mr Taylor said. But abhorrence in Northern Ireland at what had happened could be used to isolate the terrorists and involve the people in the democratic process, he urged. "That is why we believe that an election is the one way of opening up an opportunity.
The Democratic Unionist Party leader, the Rev Ian Paisley, said the tax disc on the lorry used in the bombing had been stolen from another vehicle three weeks ago, according to the RUC. "So three weeks ago the planning was going on, the premeditation was going on of this terrible carnage."
The people of Northern Ireland should "have their say" - but not through Mr Hume's idea of a referendum on chosen questions, but "on who speaks for whom at the negotiating table".
The independent unionist MP for North Down, Mr Robert McCartney, condemned Friday's attack as "an act of horrific violence". He said: "The restoration of a ceasefire and the entering into further negotiations with Sinn Fein/IRA begs the question: will they, further down the line when they meet with another impasse or some situation which does not meet with their approval, simply blast it out of the way in the manner of Canary Wharf?"