It is a kind of seven-year itch. If Gordon Brown and Tony Blair are politically 'married' and have been since Mr Blair became Labour leader in 1994, it has always been a tempestuous and difficult marriage.

Seven years on, their problems are back on the front pages and for very good reasons.

That has meant bringing in people like Charles Clarke and Patricia Hewitt, who are very definitely not admirers of the chancellor; and using his prime ministerial authority more aggressively over domestic reform issues where, in the last parliament, the Treasury often took a lead.

Mr Blair believes, probably rightly, that he will be judged by whether he has really been able to improve Britain's schools, hospitals and transport system.

He thinks, again rightly, that time is already running out. He wants everything thrown at the problems and has been busily summoning the relevant ministers.

Spending priorities

But 'everything' in this context also means money. In effect, Number Ten has been semi-publicly ordering that the government's spending priorities are in better funding for health, education and transport.

This is not quite how it looks to the Treasury.

There, Mr Brown's message has been that voters will want to see evidence of the current spending increases being better used, before more of their money is committed.

Like any chancellor, he wants to keep the pressure on spending departments. But unlike previous chancellors, he has his own agenda too - the radical reshaping of income in favour of poorer, but hard-working families, achieved through tax credits.

Behind that lies a difference of political philosophy.

The chancellor is a bit more concerned with poorer, 'traditional Labour' voters. The prime minister is thinking more about the middle class 'New Labour' voters who are angrier about rail services and hospitals.

That is a crude, incomplete distinction, a little unfair to both men - but it has a more than a grain of truth.

What that means, of course, is that the spending ministers feel that they have Mr Blair's backing at the moment and are squaring up for a fight, if need be, with Mr Brown.

'Mo' speaks out

All of this has been bubbling away behind the scenes but has been given added edge by several unrelated things.

One is the decision of Mo Mowlam, never a great fan of Mr Brown, to speak out in a BBC documentary about the relationship.

Another is the imminence of the next round of spending negotiations.

And a third is the 'war against terrorism' .

For the politics of Whitehall often seem as much courtly as democratic. Mr Blair, war leader, now comes clanking back in full armour and tugs off his helmet, to be greeted by his political courtiers who urge him to assert himself more.

At a time when David Blunkett is being busily promoted as a potential successor to Mr Blair, Gordon Brown would be inhuman if he didn't resent all this.

He is, however, a genuinely formidable operator. And what is not true is that the euro is a current problem between the two.

The chancellor's latest thinking is rather more euro-friendly than it has been and closer to the analysis of Number Ten.

Hotheads around the prime minister hope he will fire his chancellor. They argue that the arguments and the anti-Blair briefing sap energy from the government and now need to be resolved.

'Close' relationship

I would wager a hefty bet, however, that no-one says this openly to Mr Blair himself.

His relationship with Mr Brown remains close, complicated and profoundly private. He may be irritated from time to time but he acknowledges that the chancellor has had a huge influence on the government's economic success and prestige and that he remains one of the most impressive political thinkers Labour has.

It is a difficult marriage and it is going through a difficult time. But that doesn't mean, even in these lax times, that divorce is bound to follow.

It may.

There could, one day, be a walk-out onto the street, rather than another slammed door in private.

But they are likelier to stay together, if only for the sake of the 'kids' - the rather large number of Labour MPs who owe their seats to the Blair-Brown partnership thus far.