John Curtice: Voters would not welcome higher taxes to fund Mr Brown's miscalculations

Last year Gordon Brown announced a 1p increase in national insurance, thereby breaking the golden political rule of our time: "Thou shall not increase income taxes."

This year Mr Brown is gambling that growth and thus his tax revenues will soon return to the path he has mapped out, despite the recent economic downturn. Can this make any political sense?

It might have broken a political taboo, but this month's national insurance increase does seem in line with the electorate's mood. According to the British Social Attitudes survey, since the 1980s voters have consistently preferred higher taxes and higher spending to lower taxes and lower spending.

Moreover, Labour's tax rises have not quelled the public's demand for more spending. There was a slight dip in support for more spending from 63 per cent in 1998 to 50 per cent in 2000 as the Chancellor's stealth taxes kicked in. But since then support has returned to 63 per cent, even though the national insurance increase had been announced by the time the last reading was taken

Recent opinion polls confirm that the public still backs the increase even though it is just about to hit people's pockets. An opinion poll by ICM reports 64 per cent approval, while 56 per cent are in favour says a YouGov survey.

Neither is the rise particularly unpopular with those middle class voters who will have to pay most. According to ICM, 66 per cent of them are in favour, while only 61 per cent of working class respondents agree.

But these polls and the national insurance increase share something important in common – they all suggest that voters would get something in return – for example a better health service. So having taken the money the government has to deliver.

It is here that voters' doubts set in. According to ICM, just 37 per cent think the extra revenue will be well spent while a YouGov poll says only 22 per cent think the money will not be wasted. It seems voters are suspending their scepticism about the increase. If they eventually decide the health service has not got any better they may well be susceptible to arguments that some other way must be found of improving it.

Yet persuading voters that things are getting better is not an impossible task. ICM recently found a 14 point drop over the last year in the proportion believing that the NHS has got worse. And almost as many people now think public services in general have got better as think they have got worse.

This underlying scepticism helps to explain this year's gamble. For while the public might be willing to pay for a better health service they are unlikely to welcome the news that the price has gone up simply because the Chancellor has got his sums wrong. It is little wonder he decided not to admit that possibility yesterday.

If things do go wrong then New Labour's much revered reputation for economic competence could be lost. There are already signs that this is being eroded as the economy repeatedly fails to live up to the Chancellor's forecasts. As many people now trust the Tories to cope with economic difficulties as they do Labour. If the Chancellor has to come back once again and tell us that his sums were wrong – and that we have to pay as a result – it will not just be the taxes that will be resented but the mistakes that led to them in the first place.

John Curtice is a professor of Politics at Strathclyde University