The Conservatives are fast eroding Labour’s, and Gordon Brown’s, most precious and hard-won asset — a reputation for sound economic management.

The latest Populus poll for The Times, undertaken over the weekend, shows that on six measures of economic trust, the Tories are now ahead on four, and are only just behind on two. They lead narrowly on all six among women, but on only two with men. The Tories are ahead on all six measures among professionals and managers, and Labour is ahead on all six only among unskilled workers.

Such questions have, in the past, been crucial to a government’s standing. A party that is not seen as competent on the economy finds it very hard to retain power, or, when in opposition, regain office. That was true for Labour after the Winter of Discontent in 1978-79 and its electoral defeat that May. The Tories were well ahead on the economy throughout the 1980s and, apart from the odd blip, into the 1990s despite rising inflation and unemployment.

But the political shambles of Black Wednesday in September 1992 and the subsequent rise in taxes undermined the Tory lead, as long-term figures from Ipsos MORI show. The Tories’ big double-figure lead on the economy in the early 1990s moved into a deficit by 1993. But, at first, there was only a partial switch to Labour as “don’t knows” rose sharply. Mr Brown’s remorseless campaign to establish Labour’s credentials as prudent and fiscally trustworthy after he became Shadow Chancellor in mid1992 took time to pay off.

While Labour’s ratings on managing the economy improved during the mid1990s, the big rise came only after the 1997 election when Mr Brown could show that he was not reckless in office. From then until last year Labour enjoyed an even larger lead than the Tories had in the 1980s.

That is now changing. The new Populus poll — for more details see www.populuslimited.com — shows that, while a year ago Labour was ahead of the Tories on “managing the economy well overall” by 38 to 26 per cent, the gap is now just two points. Labour is only just ahead on “maintaining a stable economy”, by 34 to 31 per cent. On “taking economic decisions that are in the best long-term interests of the country rather than for short-term political gain”, there has been a shift from a six-point Labour lead to a four-point Tory lead.

However, about three fifths of the public still thinks that the British economy will do well over the next year both for the country as a whole and for them and their families. But, at 22 per cent, net optimism (those thinking the economy will do well for the country minus those do badly) is now at the lowest level since this question was first asked in 2003.

The rising tax burden and worries that public services have not improved sufficiently may be crucial. Whereas a year ago Labour was ahead by 31 to 27 per cent on “getting the balance right between the levels of taxes and of public spending”, the Tories are now in the lead by four points. This is a serious threat to Mr Brown as he defends current levels of provision, although the Tories have played the issue cautiously promising only a slower growth in spending over the next few years and no early reduction in the tax burden.

Most galling for Mr Brown is that on one of his favourite themes — putting “the economy in the strongest position to compete successfully with the growing economic challenge from countries like India and China” — the Tories are now rated ahead of Labour, by 36 to 30 per cent.

These findings are part of the story of why the Tories have moved into an overall polling lead over the past 15 months since David Cameron’s election as party leader. They also indicate potential problems for Mr Brown after he takes over as prime minister. If voters do not think Labour is managing the economy well, and that the balance of taxes and spending is wrong, then the party is in real electoral danger.

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