There may be great changes in store for Tony Blair's ministers

SUPPOSE Tony Blair suddenly woke up one morning, did a Boris Yeltsin, and sacked his entire Cabinet. He would lose some brilliantly talented individuals, starting with the Chancellor of the Exchequer. He would be uncaging some big and extremely troublesome beasts, allowing them to roam freely in the wild of the backbenches with goodness knows what consequences. But he could still a form a plausible administration.

One bonus of 18 long years in opposition is that the four successive elections since 1979 have created quite a large pool of ambitious men and women capable of running departments. It might be tricky, but it wouldn't be impossible, to draw up a list of 22 middle-ranking and junior ministers who could fill the places of a Cabinet that had been run over, in its entirety, by a bus. (To underline the point, try the same exercise with the Conservative Party.)

Which makes it rather more surprising that we are still waiting for Tony Blair's first reshuffle. Originally, Easter had been pencilled in, but that opportunity was wiped out by the cliffhanger talks on Northern Ireland. Then Whitsun was quite widely discussed within Whitehall as an alternative. Both have now come and gone, with some, no doubt unintended, consequences. One is that that David Clark and Gavin Strang have to function loyally through more gruesome months being repeatedly tipped as candidates for the chop.

Of course, there are reasons for not reshuffling now. The heavy legislative programme, compounded by the six-month EU presidency, would mean a tiresome reallocation of half-completed tasks. Alistair Darling, a clear candidate for promotion, would have to abandon the public-spending brief he holds just as the hugely complex Comprehensive Spending Review reaches its climax. And so on.

Nor is this kind of wait unprecedented; Margaret Thatcher did not reshuffle her first Cabinet until 22 months after taking office. But there are differences. The greatest of which was that she had picked her own government - which Blair cannot really have been said to have done, because of the Labour Party rule that requires the Shadow Cabinet to form the first administration after an election victory. The next reshuffle will produce a Cabinet for whose failings Blair will take much more of the credit - and, if it underperforms, much more of the blame.

But there is another consequence, intended or not, of postponing the reshuffle once again: it becomes much less credible to confine it to one or two relatively minor posts and give all the rest the chance of another year to make or break their reputations. I would reckon that Blair regards Gordon Brown, Jack Straw, David Blunkett, John Prescott, and - in the main - Frank Dobson as having starred. Robin Cook is in a category all of his own: brilliant when he is concentrating on specific tasks - such as the EU presidency - infinitely less sure when he is distracted by noises off. Beyond that the ratings are much more variable.

But reshuffles, whether they are radical or not, are not merely a matter of moving or sacking those without the required ability, charisma and popularity, and promoting those with them. Take one example. Mo Mowlam has performed heroically and imaginatively in Northern Ireland. She is the most popular politician in Britain apart from Tony Blair.

She is a certainty for promotion if and when she moves - possibly to a wide-ranging job equivalent to that of Tory party chairman. So far the assumption has been that she will remain for at least another year. But her relations with the Ulster Unionists are close to breaking point, a fact underlined by yet another attack on her by David Trimble in a radio interview yesterday. At some point she will become like an agent sent on a dangerous mission who has become inevitably compromised by her own courage and ability.

If and when she is promoted she could be replaced by Paul Murphy, widely regarded as a safe pair of political hands in Belfast. But a more sensational, and therefore more improbable solution might be to send Peter Mandelson to Northern Ireland. Most speculation has focused on whether Mandelson will be given another portfolio-free role, this time in the Cabinet, as an enforcer for the Prime Minister, firmly at the centre of power. But making him Northern Ireland Secretary might not be quite as outlandish as it seems.

It would satisfy the widespread demand from his enemies that he be given a wholly absorbing departmental responsibility to stop him interfering with those of others. By relieving him of responsibility for the Dome, it would allay fears that the project's popularity is being harmed by its inextricable association with the Minister without Portfolio. It would test him severely. And it could be presented as a sure sign that, post referendum, Blair is taking a continued and close interest in developments in Northern Ireland.

I do not think this is likely to happen. But it illustrates an important point about the twice-delayed reshuffle. The longer before it happens, the higher will be the expectations of the difference it makes. The less will the Prime Minister be able to advance the argument that his ministers have not had the time they need to play themselves in or to complete specific tasks that they have been allotted.

And the more radical a reconstruction, as a consequence, it is likely to be. Blair may be just that much more brutal in dealing with his weaker Cabinet colleagues. And just that much more imaginative in handling some of the stronger and more senior ones. The Prime Minister's press secretary said contemptuously a few months ago that reshuffle speculation was the "junk food" of political journalism. But the longer the delay the less junky the diet will prove to be.