Tony Blair does a lot for God but doesn't like to talk about it. Despite being arguably the most pious occupant of Downing Street since Gladstone, the last time he publicly discussed his faith was six years ago in a lengthy article for the Sunday Telegraph.

What was meant to be a personal Easter-time message went badly wrong. The newspaper has still not been forgiven for interpreting his comments as suggesting true Christians could not vote for a self-centred Conservative Party. Since then, the Prime Minister has been less than open about his relationship with Jesus and the influence heaven exerts on government policy.

We know that in religion, as in politics, he is a 'big tent' man. An Anglican who worships at a Catholic church with his wife and family, Blair's interest extends to all of what he calls the "Abrahamic faiths". He has read the Koran several times in the last five years and is fascinated by the common roots of Judaism, Christianity and Islam.

However, while acknowledging that religious conviction influences his decisions, there have been only occasional glimpses of what this means. There is, perhaps, an emphasis in social policy on the individual within society that is alien to Labour's traditions of collective class struggle. But the 'rights and responsibilities' template for welfare reform appears to be sourced as much in the Protestantism of other Cabinet Christians such as Gordon Brown, Jack Straw and David Blunkett as it is in the Prime Minister's own theology.

Indeed, criticism of Blair is usually along the lines that he is too pragmatic, driven by the demands of pollsters and spin doctors rather than any fundamental religious principles. Even his attempts to set out a 'third way' philosophy are widely derided as essentially a definition of what he is not, in order to reposition Labour on the political centre ground.

The Prime Minister does not abdicate leadership altogether. He vaguely signals a direction in which he might wish to go and then waits for consensus to follow. It is not a philosophy of love but of wanting to be loved. On questions like the euro, tax increases for the NHS or state funding for politics, Blair's true god appears to be public opinion.

It is no different with the Tories. As befits a minority organisation obsessed by tradition and sustained by a belief in miracles, it is on the brink of being captured by the Catholic Church.

Iain Duncan Smith is a left-footer as well as a right-winger, while many in the party, including Ann Widdecombe and Charles Moore, the editor of the Daily Telegraph, are examples of that most dangerous type of God-botherer, the Catholic convert.

Just why there is no debate about the prospect of Britain having its first ever Catholic Prime Minister is puzzling. It may be that the Conservatives are some way off electoral resurrection, but I suspect more important is the view of many people that religion does not influence politics. After all, Duncan Smith is opposed to abortion on principle and is thought to have expressed some unsavoury views about homosexuality in the past. But electoral logic dictates he appeal to younger voters and suddenly the Tory leader is coming over all tolerant and inclusive.

So, can we feel reassured that the fundamental religious beliefs of our political leaders are mere window-dressing which, even if sincerely held, are rarely expressed in a way that will affect our lives? Maybe, but in foreign affairs, the Prime Minister is not only showing a dangerous attachment to moral truth but also demonstrating that, if necessary, other people may have to die for values that he - or at least President Bush - hold dear.

After September 11, Blair spoke of a battle between good and evil. Military action in Afghanistan would be, he said, a just war. While he did not make Bush's mistake of describing the bombing campaign as a crusade, Blair had used the same phrase with impunity about the Kosovan campaign. Now, as he prepares to back an American invasion of Iraq, it is worth re-reading the Sunday Telegraph article, not least because it touches on a political decision made in the Middle East.

"[Pontius] Pilate is fascinating because he is so obviously human and imperfect, torn between principle and political reality. He commands our moral attention not because he was a bad man, but because he was so nearly a good man. One can imagine him agonising, seeing Jesus had done nothing wrong and wishing to release him. Just as easily, however, one can envisage Pilate's advisers telling him of the risks, warning him not to cause a riot or inflame Jewish opinion. It is a timeless parable of political life," he said.

Now I'm no expert on the Middle East but it strikes me that if Ariel Sharon agonised over his decisions a bit more and Yasser Arafat had advisers telling him not to inflame Jewish opinion, then we might not be in the mess we are. And who is Blair in this parable? Is he the Roman Emperor, who hankers after a bit of regime change in neighbouring Persia? Or is he the Emperor's 'chief ally'?

There may well be policies towards both Iraq and Israel/Palestine which are more right and more wrong. But the last thing any of these countries need is another religious fundamentalist wading in with his talk of "good and evil". Vote Pilate, I say.