Mr Robin Cook, who resigned from the British government yesterday over Iraq, told the House of Commons last night that he could not support a war which had neither international agreement nor domestic support.
He said that "neither the international community nor the British public is persuaded that there is an urgent and compelling reason for this military action in Iraq."
In his resignation speech, he said he believed that the prevailing mood of the British people on Iraq was sound.
"They do not doubt that Saddam is a brutal dictator, but they are not persuaded that he is a clear and present danger to Britain. They want inspections to be given a chance and they suspect that they are being pushed too quickly into conflict by a US administration with an agenda of its own.
"Above all, they are uneasy at Britain going out on a limb on a military adventure without a broader international coalition and against the hostility of many of our traditional allies."
Mr Cook said that war threatened to destroy the remarkable global coalition to defeat terrorism constructed following the September 11 attacks in the US. History will be astonished at the diplomatic miscalculations which led so quickly to the disintegration of that powerful coalition," he said.
And he warned: "The US can afford to go it alone, but Britain is not a superpower. Our interests are best protected not by unilateral action, but by multilateral agreement and a world order governed by rules.
"The international partnerships most important to us are weakened. The European Union is divided. The Security Councilis in stalemate. "Those are heavy casualties of a war in which a shot has yet to be fired."
Mr Cook warned: "We delude ourselves if we think the degree of international hostility (to military action) is all the result of President (Jacques) Chirac.
"The reality is that Britain is being asked to embark on a war without the agreement of any of the international bodies of which we are a leading partner - not Nato, not the EU, and now not the Security Council.
"To end up in such diplomatic weakness is a serious reverse."
He said: "What has come to trouble me most over past weeks has been the suspicion that if the hanging chads in Florida had gone the other way and Al Gore had been elected, we would not now be about to commit British troops."
The chief UN weapons inspector, Mr Hans Blix, had reported that the disarmament of Iraq could be completed within months by peaceful means, said Mr Cook. But news of progress in decommissioning weapons had appeared to be greeted by Washington not with satisfaction but displeasure that it might get in the way of military action.
"From the start of the present crisis, as Leader of the House, I have insisted on the right of this place to vote on whether Britain should go to war.
"It has been a favourite theme of commentators that this House no longer occupies the central role in British politics.
"Nothing could better demonstrate that they are wrong than for this House to stop the commitment of troops to a war which has neither international agreement nor domestic support."