Malcolm Rifkind: Whispering in Bush's ear has got him nowhere. Blair must find his voice on Iraq

"He can convince most people of most things, and himself of almost anything." These words, originally said of Gladstone, sum up Tony Blair and, in particular, his policy on Iraq.

Blair must be aware that, both in Britain and throughout the world, his unconditional support for President Bush has led to the despair of his friends and the derision of his enemies. He is no masochist and he remains preoccupied with his own political survival and his place in history. He must therefore have persuaded himself, despite all the evidence to the contrary, that American policy is wise and more likely to succeed than any other.

It is the only way one can explain why the Prime Minister's political instincts and judgements, which were impeccable for his first few years in power, have been not only wrong but, also, destructive to his reputation and political authority since the beginning of the Iraq crisis.

It need not have been so. I happen to believe that the Iraq War was both unnecessary and undesirable. But even if the Prime Minister considered it to be justified he displayed inexperience and poor judgement in his handling of the crisis. He gave the President an unconditional assurance that Britain would be on side if the United States decided on war. At the same time he was assuring the British public that a second UN Security Council resolution would be needed.

This was not deliberate deception. Blair had convinced himself that his skill and charm would ensure that the Security Council would deliver a second resolution. He was wrong. In the same way he believed that by going to Damascus he would persuade the Syrians to drop their opposition. Again he was wrong. All he received for his pains was a humiliating dressing-down by President Assad in public.

His mistake was to know little of British history and to reject the views of his diplomatic advisers. In the past our excellent relations with the US have never required unconditional support for the White House. You could not get more pro-American than Margaret Thatcher but it is well known that she ferociously attacked Ronald Reagan over the US invasion of Grenada and not just in private. She used the BBC World Service to vent her indignation. Harold Wilson refused Lyndon Johnson's request to send British troops to Vietnam without lasting damage being done to relations across the Atlantic.

Downing Street would have us believe that the Prime Minister prefers to make his vigorous representations in private. But Sir Christopher Meyer, until recently our ambassador in Washington, and present at many of the meetings between Blair and Bush, has said publicly that Blair has not been robust or insistent, even in his private representations.

It is not too late. If the Prime Minister wants to redeem some of his reputation the next few weeks will be crucial. The Americans have lost so much support throughout the world that they could not afford to lose the British as well. Blair, therefore has the maximum leverage if he is willing to use it.

He should insist that continuing British support will require three commitments from Washington. First, it is more important that the Iraqis to whom sovereignty is transferred at the end of June are acceptable to the Iraqi people than that they are friends of the Americans. Only when the Iraqis believe that they are being governed by their natural leaders and not by the US will the insurgency die down and some stability return. This does not mean that coalition troops should withdraw. That would be disastrous, and the Spanish government has been foolish to order its own troops out. But the coalition forces must answer to the Iraqi government and not just to the coalition forces.

Second, for as long as a foreign army is needed in the country it must have the legitimacy that can best be conferred by a new United Nations resolution. But that will not be possible without French, Russian and other support in the Security Council. President Bush needs allies but they will only be available if he is willing to share power. The British Government should make that clear.

The third requirement is that responsibility for nation building must be removed from the Pentagon and Donald Rumsfeld. The Pentagon's experience and skill are in winning wars, not winning the peace. That is for statesmen and diplomats. The responsibility, under the President, should be transferred to Colin Powell and the State Department.

If Tony Blair made these the conditions for continuing British support there is every likelihood he would succeed. If whispering them into the President's ear doesn't work, he should shout them from the rooftops. In current circumstances, that would be real leadership.

Sir Malcolm Rifkind was the Foreign Secretary from 1995 until the 1997 election. In February, he was selected as the prospective Conservative candidate for Kensington and Chelsea