John Curtice: This snapshot shows the scale of Brown's task

Gordon Brown is proposing to fight the forthcoming election on some of his famous "dividing lines". He hopes to persuade the public that Labour will protect public services while the Conservatives would cut them. And he aims to contrast his party's support for those on "middle and modest incomes" with the Conservatives' concern for the privileged few.

But Mr Brown can only profit from such an approach if his side of the alleged dividing line is clearly the more popular. And the latest findings from NatCen's British Social Attitudes survey cast doubt on whether the public will be as receptive to the arguments that Mr Brown is hoping to deploy as they might have been a decade ago.

There have been two key changes in the public mood. First, voters have apparently come to the view that the increase in spending on public services under Labour should come to a halt. Just 39 per cent want more spending on services such as health and education and are willing to pay increased taxes to meet the resulting bill. This is well down on the 63 per cent that took that view in 1998, shortly after Labour came to power.

Indeed support for tax and spend is now at its lowest level since 1984, when Thatcherism was at its height. In such a climate, Tory claims that spending can be cut by cutting "waste" could well prove persuasive.

Second, in moving Labour on to the centre ground, the New Labour project has seemingly undermined public support for traditional Labour values – such as a more equal society. For example, only 38 per cent now agree that "the Government should redistribute income from the better off to the less well off", far below the 58 per cent who favoured that proposition in 1993, just before Tony Blair became Labour leader.

One of Mr Brown's favourite words, "fairness", may no longer have the resonance for voters he presumes it has.

Still, even if Mr Brown may no longer have particularly popular tunes, he might still hope to revive his party's fortunes by appealing to the loyalty and affection that some voters still have for his party. Alas, it seems that this is now in short supply too.

Just 27 per cent of voters now regard themselves as long-term Labour supporters. As recently as 2005 no less than 40 per cent were willing to say they were members of the Labour tribe. Indeed, at 32 per cent, those who consider themselves "a Conservative" outnumber those who say they are "Labour" for the first time since 1989.

It seems this spring Mr Brown will face a public that is both out of love with his party and out of love with its message. He has a tough task indeed.

John Curtice is a research consultant to NatCen and professor of politics at Strathclyde University