John Rentoul: Adair Turner has a tin ear for practical politics. Brown and Blair will see him off

Since he is not fighting the next election, he is simply off on a frolic of his own. He does not much care about the Labour Party, and is going to do whatever he wants to do. So says one astute observer of British politics. This "frolic" is going to lead to yet more conflict with Gordon Brown, who has to restrain Tony Blair's increasingly desperate attempts to leave a mark other than the scratches of fingernails on the edge of the black door of No 10.

That, then, is the context for the revival of tensions between Blair and Brown, particularly over the pensions crisis. Except that it is not. The astute observer of Blair's "frolic" is in fact the Prime Minister himself, in an interview this month, as he described "the argument that is being run against me".

An unholy alliance of the Conservative party, the Labour "ne'er-do-wells" as Charles Clarke called them after the Terrorism Bill rebellion, and elements of the media were conspiring in "an attempt to decouple me from the Labour Party", Blair said.

He is right, and it takes only a moment to understand the motives of the conspirators. David Cameron is much the most able strategist to contend for the Conservative leadership since the fall of Margaret Thatcher. In his debate with David Davis on ITV last weekend, he laid into the idea that the Tories should "go through the division lobbies with Frank Dobson and Jeremy Corbyn and people who, frankly, if you put them in the Natural History Museum, the dinosaurs would walk out in objection".

His objective is to hug Blair close, support his radical reforms of the public services and identify Brown with the Dobson-Corbyn tendency. Then, if and when the Chancellor takes over, he will be hailed as the leader of the Late Cretaceous Party.

And the Cretaceans themselves are happy to assist the Tories in this, by comparing Blair to Ramsay MacDonald in his willingness to go into the division lobbies with Cameron. Jon Trickett, the Labour MP, says in the New Statesman this week he is not bound by the manifesto on which he was elected because the schools policies in it were "lifted" from the Tories.

Then there is the journalistic interest in "decoupling" Blair from Brown. The tensions between the two have been a staple of political reporting since 1994 and it is hard to break old habits. Blair does regard the pension credits system - as Turner seems to - as too complicated and bureaucratic. So when war broke out between Gordon Brown and Adair Turner, who publishes his report on pensions reform on Wednesday, it was tempting to assume that the Prime Minister would take Turner's side. After all, Blair appointed him, and Brown's people last week blamed Blair's people - the "teenage Taliban" - for leaking the Chancellor's letter that cut the ground from under the Turner commission's feet.

Tempting, but wrong. Such an analysis overlooks the powerful forces binding Blair and Brown together in this third and final phase of the Blair premiership. Something changed in their relationship in the weeks before the election. Call it a deal if you like, but it was no more formalised or recorded than the ambiguous compact made at the Granita restaurant 11 years ago. It was a recognition of mutual interest: that Blair's legacy and Brown's inheritance would be secured if they "stuck together", in the words of someone familiar with the discussions.

This is primarily a battle between Brown and Turner, but the Prime Minister is on his Chancellor's side. Not least because the two politicians understand politics better than the former McKinsey's management consultant. Until Turner was drafted in to the Prime Minister's short-lived Forward Strategy Unit four years ago, his main experience of politics was as head of the CBI. As Digby Jones, his successor, confirmed last week, that job consists largely of calling for tax breaks for business before every Budget and Pre-Budget Report.

So no wonder the main points of Turner's report leaked early reveal a tin ear for the politics of the possible. Raising the state pension age to 67 is, of course, sensible and, at one level, most voters recognise it as such. But it feeds too easily into an unthinking caricature of a government that makes people pay more taxes and work for longer with less to show for it at the end. A more "political" report would have gone for a flexible retirement age, allowing people to choose between retiring earlier or taking a higher pension.

A more "political" report would have taken a different tack, too, on relinking the state pension to earnings rather than prices. That is a battle that Brown - strongly supported by Blair - fought and won in the first term.

Brown's refusal to bow before an emotional campaign led by Barbara Castle, incidentally, makes a mockery of the idea that he is somehow with the Dobson-Corbyn wing of the party. Brown's job as Chancellor is to keep control of the costs that will fall on the taxpayer.

The same applies to nuclear power: his scepticism is nothing to do with being greener than Blair (most of the evidence would have them the other way round), but with the fiscal bottom line.

Attempts to discern ideological differences between Brown and Blair on the other difficult issues coming up are similarly doomed to failure. The really seismic issue is education. But the word from Number 11 is that Brown is fully behind the schools White Paper. It is not in his interest to be seen as the defender of a status quo that serves so many children badly, especially in poor areas.

Other issues are less threatening. If education is rated by Downing Street at 7 or 8 on the Labour Party's Richter scale, nuclear power was judged to be a 4 or 5. But an MP charged with taking soundings reported back to the Prime Minister that, in his opinion, it was a mere 2 or 3.

Replacing Trident will not separate Brown either. Nor will reform of incapacity benefit. It was Brown, after all, who was responsible for the first wave of welfare reform - and, incidentally, the first big Labour back-bench rebellions - on lone parent benefits in the first term.

On all these long-term issues, a simplistic view might be that Blair has "no dog in this fight" as Bill Clinton might put it. Again: not so. Blair knows his reputation would be harmed by dodging the hard choices, to leave his successor to pick up the pieces. Turner should have realised, before he took on the Chancellor, that Blair and Brown are in this together until the handover.