Mr Blair's most loyal supporters can stop him going to war in Iraq

Rumours are that a growing number of 'doves' in the Cabinet are angry that Mr Cook has taken such a high-profile stand

The theory of cabinet government has been a staple of every university degree course on British politics for successive generations of students. In its purest form, the principle rests upon the assumption that the Prime Minister is merely first among equals. Subjects are brought to the attention of the Cabinet according to the need to reach a collective decision. Ministers are free to argue the pros and cons around the table before a decision is taken.

The Prime Minister invariably has a particular view and seeks, in his summing up of the discussion, to influence dissenting voices to obtain consent. Once the collective decision is taken, all cabinet ministers are signed up to the policy with varying degrees of enthusiasm. If they still insist on making their dissent public, beyond the confines of the Cabinet Room, convention dictates that they resign. No formal vote is taken – at least in public. Ministers who may have been outnumbered in the discussion are supposed to do the media round, loyally commending a decision with which they have misgivings, to prevent the headline "Cabinet split".

Under this Government, there have been no cabinet resignations on any matter of principle since Tony Blair took office in 1997. We can read this in three ways. Either the Cabinet is one of the most united in political history. Or the Cabinet is simply made up of poodles who do what Mr Blair tells them. Or, lastly, dissenters who could not be relied on have simply been purged. There have been a remarkable number of dismissals, but none has been because of serious policy disagreements.

The reality is more complicated. We know that there are personality clashes between various ministers – although they are often more to do with the mechanics of policy rather than on policy itself. Rivalries, jealousies and jockeying for position in the event that the Prime Minister falls under a bus provide the material for alleged disagreements.

Enoch Powell claimed that, in its purest form, collective cabinet responsibility ended during Margaret Thatcher's premiership. Apart from the John Major interlude where, supposedly, a collegiate form of cabinet decision-making was re-instated, the view is that Tony Blair has further eroded the collective process with cabinet meetings no more than brief formalities, ratifying bilateral decisions taken by the Prime Minister and individual cabinet ministers most concerned with a particular aspect of policy.

The question is whether it will be the Prime Minister, the Cabinet or Parliament that will take the decision on whether to join the United States in any war with Iraq. Fears are understandably expressed that the Prime Minister will do what President Bush asks of him without the authority of Parliament or the Cabinet. The Crown prerogative enables the Prime Minister, constitutionally, on behalf of the sovereign and in the name of her government, to undertake military action without asking for Parliament's consent. Many are concerned that Mr Blair might use this prerogative to prevent Parliament and the Cabinet expressing an opinion until after military action has commenced.

But it is inconceivable that Mr Blair would take such action without the clear and unambiguous support of his cabinet colleagues. He would surely want to do everything to avoid even one resignation. So we can be fairly certain that all cabinet ministers will have their say in a cabinet debate before final decisions are taken. Which is why it is a little difficult to understand why so much fuss is being made about the role of Robin Cook, the Leader of the House, whose friends report that he is the ringleader of the dissenters. My respect for Mr Cook as Leader of the House knows no bounds. He has become a genuine champion for backbench MPs.

But Mr Cook must know that he may be past the half-way mark of his ministerial career and that many will therefore question, rightly or wrongly, his motives. The suspicion must be that the publicity around him has as much to do with extending his tenure in government by posing as a champion of Labour backbenchers – thus making himself unsackable. Rumours are surfacing that while there are a growing number of "doves" in the Cabinet, they are angry that Mr Cook, through his emissaries, has taken such a high profile.

Earlier this summer, to coincide with the 20th anniversary of the Falklands war, the former defence secretary Sir John Nott published one of the best insights into the stresses and strains of serving in the Thatcher cabinets. He describes disagreements on fundamental issues, such as her government's economic policies. Cabinet meetings were far different from the image of a domineering Prime Minister with docile backing from cabinet poodles. What is clear, from his recollection, is that the restraining influences in curbing Margaret Thatcher's over-enthusiasm came from those normally thought of as "one of us", rather than from those who were renowned for their hostility. Similarly, it will not be Mr Cook or Clare Short who will make the difference in moving this Cabinet into a "dove" position. More likely, it will be the ministers with the most "Brownite" or even "Blairite" credentials.

Not that Mr Blair is as gung-ho for war as perhaps he has been painted. His constant refrain that no decisions have been taken might be an indication that he is actually dreading the White House hotline bursting into life from the other side of the Atlantic, with President Bush suddenly drawling, "Tony, we go in tonight". But this is a moment when, for the first time in the history of this Government, cabinet discussion can make a difference. It will be the Prime Minister's most loyal cabinet supporters, however, rather than known sceptics, who will have the most sway.

The Chancellor has an obvious reason to be extremely concerned about any open-ended financial commitments to a project that could wipe out the whole of his contingency reserve. He will be making the case, as he did over Kosovo in 1999, that any costs should be borne from existing departmental budgets. This means that the burden would fall on the Ministry of Defence. If this message is already being sent, privately, to the Defence Secretary then an otherwise important Blair ally, Geoff Hoon, will be among the doves.

Alternatively, the Chancellor could intimate to Paul Boateng, his newly promoted Chief Secretary with impeccable Brown and Blair connections, that he will be expected to ask spending ministers to yield savings from their budgets to pay for such an undertaking. This would ensure that both Mr Boateng and big spenders such as the Health Secretary, Alan Milburn, or Transport Secretary, Alistair Darling, would be lukewarm about military action.

For once, the theory of cabinet government will, this time, be seen to be fully operational in practice. The Prime Minister will be merely one voice among other cabinet equals. But the doves that will matter are not necessarily those led by Mr Cook.

mrbrown@pimlico.freeserve.co.uk