Tony Blair is facing a political storm, but this could also be bad news for Gordon Brown

If the hallmark of an effective politician is an ability to control the political weather, then Gordon Brown certainly looks to be in a stronger position than Tony Blair at the moment. Last week, the Chancellor was in the Vatican, exhorting a conference of international church and government leaders to give more aid to developing countries. He also found time to deliver an erudite lecture on what it means to be British. And today, the Chancellor will unveil his comprehensive spending review to Parliament, in which he will triumphantly propose to lavish yet more funds on the public services.

If the hallmark of an effective politician is an ability to control the political weather, then Gordon Brown certainly looks to be in a stronger position than Tony Blair at the moment. Last week, the Chancellor was in the Vatican, exhorting a conference of international church and government leaders to give more aid to developing countries. He also found time to deliver an erudite lecture on what it means to be British. And today, the Chancellor will unveil his comprehensive spending review to Parliament, in which he will triumphantly propose to lavish yet more funds on the public services.

Compare this with the Prime Minister's situation. Over the next five days, he will have to deal with both the Butler report, which is expected to be critical of the Government's use of intelligence in the build-up to the invasion of Iraq, and two by-elections, which look unlikely to deliver a favourable result to Labour. Thanks to his ill-advised Iraq adventure, the political weather is proving decidedly inclement for the Prime Minister; Mr Blair's primary objective will be to get through the week.

It is a small mercy for Downing Street that today's spending review will put the focus on domestic issues, if only for a short while. The Chancellor will attempt to pull his usual trick of appearing generous and prudent at the same time. And he will produce long lists of figures to show that spending on key public services will rise. But the centre piece of this spending review will be cost-cutting measures. The Chancellor will reveal Sir Peter Gershon's long-awaited report into the public sector, which, we are told, will identify 80,000 job cuts and point out how efficiency reforms can save the public purse £20bn by 2008. Mr Brown will attempt to convince us that by saving money the Government can spend more on key services, but avoid raising tax. This would undoubtedly be a neat solution, although it has to be pointed out that every politician under the sun has proposed the same thing. And after a significant expansion in the size of public sector bureaucracy, one has to ask why it has taken so long for Mr Brown to turn his attention to cutting out waste and improving efficiency.

But perhaps the greater significance of the spending review, for the Chancellor's supporters, is how it makes Mr Brown look in comparison to Mr Blair. While the Chancellor demonstrates his mastery over the growing economy and confidently sets out his economic stall for the next four years, Mr Blair is fighting for his political life. And Mr Brown's ambitious acolytes will hope the weekend rumours that the Prime Minister was on the verge of quitting only a few weeks ago are true rather than a convoluted way of restating his appetite for the job.

The reports emerge as Mr Blair's ill-fated decision to exaggerate the threat posed by Saddam Hussein returns to haunt him in the form of the Butler report on Wednesday. Thursday's Birmingham Hodge Hill and Leicester South by-elections will be interpreted as mini-referenda on the Prime Minister. If things go badly for Labour, as predicted, the chorus of internal opposition to the beleagured Prime Minister will intensify.

Events across the Atlantic also seem to be conspiring against Mr Blair. The Democratic team of John Kerry and John Edwards, emboldened by the Senate report's damning criticism of the CIA, has accused President Bush of misleading the American people over Iraqi WMD. This will do nothing to help the President's most conspicuous ally when he faces his own intelligence report from Lord Butler. The US election campaign is hotting up at just the wrong time for the Prime Minister.

But the game is not yet over for Mr Blair. Although Mr Brown seems to be controlling events more effectively, this alone will not be enough to dislodge his neighbour. And any undermining of the Prime Minister simply impedes the Government's ability to drive through much needed reform of the public services. Mr Brown may find that a political storm that causes problems for his leader may wash away his own achievements in the process.