Sean O'Grady: Going to war with Iraq could bring Blair the mother of all party splits

One of the more remarkable features of the Blair government is the way that it has survived more than five years in office without a single resignation by a cabinet minister on an issue of principle or conscience. That enviable record may be about to change. There have always been a few cabinet ministers who have had the air about them of a resignation waiting to happen. And these putative rebels may be about to find their cause: Iraq.

Robin Cook is supposed to be so unconvinced about the merits of a military intervention to remove Saddam Hussein that the only role he is prepared to countenance for Britain is to permit the United States to use the air base at Diego Garcia in the Indian Ocean as a staging post. Clare Short, Secretary of State for International Development, is thought to share those concerns. It is claimed that the Chancellor, Gordon Brown, is worried about the impact of a war on the world economy. And the Defence Secretary, Geoff Hoon, has apparently encountered the characteristic caution of the military chiefs. Jack Straw is sometimes tossed into the frame as well. Not to mention the indefatigable resistance of the likes of Tam Dalyell, Gerald Kaufman, Chris Smith, Tony Lloyd and Glenda Jackson on the back benches.

The TUC conference next month is likely to back a resolution proposed by the National Union of Journalists opposing a war on Iraq, and the Labour Party conference will be a rough ride. The coalition of forces facing Tony Blair within his own party now looks somewhat more impressive than the one facing Saddam – the mother of all party splits, one might say. The Americans like to give their military operations vivid code names such as "Operation Eloquent Banquet" or "Operation Desert Storm". The Labour rebels should think of one too: "Operation Caged Poodle".

The source for much of this intelligence is Mark Seddon, editor of the socialist weekly Tribune and member of Labour's National Executive Committee, who, oddly, chose to make his knowledge public through the columns of the Tory-inclined Spectator. At any rate, Mr Seddon is in earnest, writing that: "Tony Blair could yet find himself looking around the Cabinet table for support, only to find many of his ministers shuffling their papers and avoiding his eye. If one were to speak out, he would become the darling of the Labour movement; and he – or she – would be followed by others."

That parenthetical "or she" points clearly, and unsurprisingly, to Clare Short, although it would be fair to say that Mr Seddon's remarks read more like a wishful invitation to defect than a confident prediction that she will. Still, she's the girl most likely to jump. She has resigned over Iraq before, as one of three Labour frontbenchers who quit over Neil Kinnock's support for the first Gulf War in 1991 – an operation that actually did have UN backing. Ms Short has certainly made no secret of her unhappiness with current policy. As recently as March she told John Humphrys on BBC1's On The Record: "The best thing is to get the UN inspectors back there, but there isn't crude military action that can deal with the problem of Saddam, and with the state of the Middle East and the terrible suffering of both the Israeli and Palestinian people. With the anger there is in the Arab world, to open up a military flank on Iraq would be very unwise." Pressed on resignation, she added: "Yes, I am the same old Clare Short, and I'm proud to be a member of the Government, but I've got lots of bottom lines. I don't expect the Government to breach them, but if they did I would [resign]. That's what you should be like in politics, I think." Not exactly coded.

As for Mr Cook, he too has a past, but a less promising one for a potential rebel leader. In 1991 he was a middle-ranking member of Mr Kinnock's shadow cabinet, and against that conflict. However, he did not quit, and stuck to the convention of collective responsibility. During his five years as foreign secretary under Mr Blair he went on to organise many of the military operations that so enraged the left. So close was he to the American secretary of state, Madeleine Albright, that she was called the "third woman in his life".

His greatest service to the "special relationship" were his efforts in the UN Security Council to secure backing for Operation Desert Fox, the bombing of Iraq in 1998. This is what he said: "Here is the link between our opposition to Iraq and an ethical base to foreign policy. We have taken a very strong line against nuclear, chemical and biological weapons. It would be totally inconsistent with that if we were to allow Saddam to remain in possession of weapons of mass destruction." What, you might ask, is so very different now, except that Mr Cook has since been sacked as foreign secretary and is no longer in charge of the policy?

Mr Blair's instincts about internal dissent can be roughly summed up as follows: that if he had a pound for every time people told him that he'd lose a parliamentary or conference vote or have cabinet members walking out on him he'd be a very rich man. Ms Short, after all, sat in Cabinet through the 1998 bombing of Iraq and the American-led operation in Afghanistan, daisy-cutters and all. It probably won't happen, but even if she and a few junior ministers did quit, he rightly calculates that he could cope with that level of collateral damage.

But he cannot be so blasé about the Chancellor. Thus far, Mr Brown has resembled Macavity the Mystery Cat, notably absent or quiet when the Prime Minister has been embroiled in some foreign adventure that Mr Brown judged imprudent. Unsupportive as some think him, this cat has not yet been actively hostile, although he has let it be known he thinks Mr Blair's approach a little too "gung- ho". The real difficulty arises not from resignations but if the Brown-Short-Cook axis uses the leverage that a sceptical party and public gives them to resist the whole policy.

Such a move would leave Mr Blair in roughly the position Harold Wilson found himself in during the Vietnam War in the 1960s: able to offer an American president limited diplomatic cover, but absolutely no involvement by British forces. Another war on Iraq may not happen, if support for it in the Bush administration and the wider Republican Party continues to weaken. But if it does go ahead, and if Mr Blair is unable properly to support it, that would destroy his relationship with George Bush and leave the Prime Minister in a weak, possibly untenable position. Never mind Clare Short; what's Tony Blair's bottom line?