Adair Turner, head of the government’s Pensions Commission, says lower-paid workers could, however, still retire on a full pension at 65 to reflect their lower life expectancy.

The move would break the century-old system of a common state pension retirement age across all social groups and shows how the scale of the problem is forcing Whitehall to consider drastic measures.

It would mean the professional middle classes would bear the brunt of what Turner describes as the “tricky choices” forced onto the government by the ageing population.

But he argues that such a radical change might be necessary because professionals survive on average five years longer than lower social groups after retirement. Turner says this should be reflected in the state retirement age. “One of the sad facts is that although life expectancy is going up, it is going up least in lower socio-economic groups,” Turner said.

“So we have to be sensitive to that when we put up the state pension age. For example, the person who starts work at 16 would be able to get something at 65. The person who went to university and started serious work at 23 is not going to get it until 70.”

In the interview, Turner said that all workers might have to be forced to save for a pension with the money invested on their behalf by the government. It would ensure that everybody would have an annual income of about £12,000 a year, including the basic state pension.

The unpopular changes are being considered by Turner because of the multi-billion-pound shortfall in the amount that people have saved for their retirement. Estimates have put the shortfall at between £30 billion and £60 billion.

During the election campaign, Labour said that it would decide how to reform pensions after receiving Turner’s final recommendations in the autumn.

David Blunkett, the new work and pensions minister, has already accepted that people will have to retire later and pay higher taxes to fund more generous pensions. Sources close to the minister said that they were looking at Turner’s proposals and had not ruled out a “flexible retirement age” in future.

Turner has proposed a two-tier system because he believes that a more sophisticated approach to increasing the state pension age is required.

“We’ve got to be wary of saying, ‘Well, in order to get our numbers to add up without a further tax increase it (the state pension age) has got to be 70 in 2030, end of story’. It’s too cavalier in relation to the life expectancy of people at the bottom end of the income scale,” he said.

Ironically, the wealthy are far more likely to retire earlier. They would still be free to do this but may not receive any state support until the age of 70.

Frank Field, former Labour welfare reform minister, said: “I think the idea is wonderful, but how do you make it a practical policy?” Sir Malcolm Rifkind, shadow work and pensions minister, said: “Changing the entitlement depending on whether you went to university would not only be wrong in principle but almost certainly unworkable.”

Although Turner is still working on the detail of his recommendations, last week he gave an outline of his likely solutions. He is working closely with Blunkett and the government is expected to set out its broad framework for reform on June 21.

“We are clear that there is not a coherent long-term pensions system. It is agreed that the state ought to make sure by some means that everybody is out of poverty in retirement. The problem is there’s not enough money. Remember, underlying this there is no free lunch. There are more people living longer and (that) . . . means there are some tricky choices about sums of money,” Turner said.

“I can’t go through the figures at the moment, the numbers don’t add up which is why you might need some extra (National Insurance contributions).”

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