London Briefing:  The Turner report on the reform of Britain's pension industry is finally due to be published today, but we already know its broad outlines.

Controversy has been sparked by a leak - supposedly from sources close to Tony Blair - giving details of Gordon Brown's opposition to one or two fiscal consequences of Lord Turner's conclusions.

One of the smartest moves the Treasury ever made was to link state pension payments to prices rather than earnings - pay tends to increase at a faster rate than retail prices. The taxpayer has saved billions at the expense of the pensioner. Now, apparently, Turner wants to restore the connection with earnings.

That such a proposal would be killed stone dead by the chancellor should have been immediately apparent, and suggests that the Pension Commission has either been badly advised or is a touch naive. Its credibility will not be enhanced with a recommendation that stands no chance of being implemented.

Turner is expected to argue for a rise in the retirement age to 67. This is both sensible and inevitable. Indeed, 67 is still far too low, given the fiscal consequences of current demographic trends.

That we are living longer is well known, but it is the acceleration in longevity that is taking demographers and actuaries by surprise. Pension promises made in the last few years are not going to be honoured.

Many headline writers seem to think that the pension crisis is something that has crept up on us suddenly. It is in the nature of such things that they happen incrementally and over long periods of time.

This problem has, in fact, been building for years - and its effects are still to be felt in a material way. Our taxes are not - yet - rising to meet higher pension costs, and there have only been a few cases of company schemes going bust. It is to the government's credit that they are trying to do something about a problem that is yet to bite in any significant way.

Blame for the pension crisis is variously laid at the door of Brown's previous tax "raid" on pension funds, poorly performing stock markets and nasty corporations closing their "defined benefit" retirement plans.

It doesn't help, of course, that the vast majority of us hardly save anything at all, let alone enough to fund 20 years or more of comfortable retirement.

All of these things have contributed to the problem, but they really don't amount to much compared to the simple fact that we are living longer. It wouldn't make much difference if taxes on pension funds were cut, and few people will ever be able to save enough for decades of retirement.

The arithmetic of the pension problem is such that even if firms were legally obliged to reopen their defined benefit pension plans on the same terms, most of those businesses would, as a result, eventually go bust.

But it is to the government's eternal shame that they have kicked off the most recent round of the debate with an appalling decision to allow the current generation of 20-somethings in the public sector to retire at 60. It makes no fiscal sense and offends everyone's sense of fairness. Just a few weeks after Blair caved in to the public sector unions, the government-appointed pension commission now has to make the case for everybody in the private sector to work for longer.

The Turner report is supposed to kick-start a debate that is likely to go on for years. Brown has got his retaliation in early, laying down a very sensible marker that flags a no-nonsense attitude to the problem.

Just as companies cannot pay for pensions, neither can the government. In fact, nobody can: by 2050, nearly a third of the UK population will be over 60.

On the current rules, all those people will either be reliant on the state or the taxpayer for their incomes - an utterly unsustainable situation from an economic and social perspective.

It could, of course, be worse. By 2050, more than 40 per cent of Italians will be over 60. Lesser problems have caused revolutions.

Experts witter on about dependency ratios: the number of workers supporting each pensioner. Suffice to say that these ratios are getting worse, particularly so in countries like Italy and Japan. Even China is getting in on the act.

To put the problem in perspective, let's consider the sums that we know can't be afforded. Britain cannot afford to let the current pension grow in line with average earnings: the country will go bust. That pension, which must, therefore, be forced to fall relative to earnings, is currently £131.20 (€191.59) per week for a couple, £82.05 if you are single.

Chris Johns is an investment strategist with Collins Stewart. All opinions are personal.