As the Prime Minister arrives in Australia, there are plenty in Britain willing him never to return, to Downing Street at least. Labour’s loans scandal has marked open season for many and varied malcontents, mischief-makers and the occasional principled critic. They demand decapitation and their reasons range from disgust to boredom. Amid the froth, some of the arguments advanced for handing over to Gordon Brown this summer are almost plausible. But it is rarely wise to take long-term decisions fuelled by transient indignation.

Mr Blair’s mistake in soliciting loans from wealthy benefactors and hiding them from the regulatory machinery he himself established was grievous, the worst of his premiership. He has given impressive ammunition to those who doubted that he ever was the “pretty straight sort of guy” he professed to be. Moral dishevelment is not easily tidied from the record. But he has paid a heavy price and he is not alone in having sinned. The Chancellor’s day in the sun this week, when he looked comfortable around the levers of power, has further emboldened those insisting on change. It is not clear, though, how this would be in Mr Brown’s own interests and it would certainly not be in the country’s.

However much the Chancellor’s pulse quickens at the thought of his 12-year wait for the party leadership ending, he should still bide his time. The aftermath of disastrous local election results, for which Labour is braced in May, would not be a propitious moment to inherit the crown. It would also suit Mr Brown if Mr Blair cleared up the party funding mess himself. And the more of a prime ministerial record Mr Brown builds before the next election, the less inclined voters will be to give him the benefit of the doubt.

Such issues are tactical considerations. The larger point is that satisfying the yearnings of a minority of the Parliamentary Labour Party and sections of the London-based commentariat is vastly different from doing your duty. The notion that Mr Blair has reached a “tipping point” is alluring but over-excited. There remains much he can do and much to do.

Amid the avalanche of negative headlines it is easy to forget the Prime Minister’s political skills. Despite the recalcitrant rump on Labour’s backbenches, there are far-reaching issues of substance on which his input is desirable — pensions, energy policy, education and rebuilding Iraq. But he can make the biggest difference in his strongest suit: shaping debate on the largest questions. His series of speeches on terrorism is a case in point. Mr Brown has so far shown no grasp of the singular importance of defeating extremism, nor how to approach such an issue. In similar vein, Mr Blair, better than anyone, can influence how Britain approaches the nexus between economic growth and environmentalism, one of the key challenges of the coming decades. He should travel to India twice in the next year and help its leaders to feel their way on to the world stage. And he must continue to drive the reform agenda in Europe.

The political realities of Mr Blair’s decision to “pre-resign” mean that he could never hope to serve more than half a third term. Britain’s interests, and those of government and party, would be best served if the Labour conference in the autumn of 2007 saw a new leader on the podium. In the meantime, Mr Blair should remain an active, liberalising, reforming prime minister.