"The reality is that Britain is being asked to embark on a war without agreement in any of the international bodies of which we are a leading partner - not NATO, not the European Union and, now, not the Security Council.
To end up in such diplomatic weakness is a serious reverse.
Only a year ago, we and the United States were part of a coalition against terrorism that was wider and more diverse than I would ever have imagined possible.
History will be astonished at the diplomatic miscalculations that led so quickly to the disintegration of that powerful coalition.
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.
Yet tonight the international partnerships most important to us are weakened: the European Union is divided; the Security Council is in stalemate.
Those are heavy casualties of a war in which a shot has yet to be fired.
I have heard some parallels between military action in these circumstances and the military action that we took in Kosovo. There was no doubt about the multilateral support that we had for the action that we took in Kosovo.
It was supported by NATO; it was supported by the European Union; it was supported by every single one of the seven neighbours in the region. France and Germany were our active allies.
It is precisely because we have none of that support in this case that it was all the more important to get agreement in the Security Council as the last hope of demonstrating international agreement.
The legal basis for our action in Kosovo was the need to respond to an urgent and compelling humanitarian crisis.
Our difficulty in getting support this time is 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.
The threshold for war should always be high.
None of us can predict the death toll of civilians from the forthcoming bombardment of Iraq, but the US warning of a bombing campaign that will "shock and awe" makes it likely that casualties will be numbered at least in the thousands."