Urging us to start a debate about tax is a strange thing to find as the centre-piece of a Labour chancellor's agenda. Isn't that one of the main questions political choice was always supposed to be about? Gordon Brown unfurls the issue after seven years spent keeping it tightly wrapped. Not having the debate has been at the heart of his political strategy. Such silence about a key mechanism of what we used to call socialism has been apparent all round the western world, a by-product of the left-right stasis that settled over the 1990s. But nowhere was the possibility of a pro-tax position further beyond the pale than in the realm of New Labour.  In Britain, Mr Brown and Mr Blair implied, the issue was settled. Thatcherism had established the new norm, from which they would not depart. Their commitment against higher direct tax rates, and their decision to freeze public spending for the first two years, were meant to close down the fundamental argument. In reality, all kinds of taxes were pushed up. There was a welcome shift on another left-right axis, the pattern of redistribution. But debate was precisely what was not allowed. These things happened by stealth. Any possibility that public opinion might favour higher taxes openly proposed was too alarming to put to the test. It might tear apart the image of a reformed Labour party. Political convenience dictated that debate should not occur.   Now political convenience says differently. The leaders invite a discussion because they see the need to raise taxes, including perhaps direct taxes, which they've previously promised not to touch. Moreover, a cynic might say, they've loaded the outcome in their favour. Some public services have reached such a depth of inadequacy, in the fourth largest economy in the world, that there can be no case against greater public spending, or therefore higher tax. We've been living for five years in the middle of a social experiment that might have been designed to prove that the low-tax, low-spend aspirations of Thatcherism had finally to be contested. It's unnerving to think that the impoverishment of the NHS may be the only way a progressive party could get its case across. But that has surely helped precipitate Mr Brown's uncharacteristic request for a debate.   Meanwhile something else has been happening. The argument may at last be urgent, but it will be harder to have. There's a new dimension since the early days of Mr Blair. Public confidence in politicians seems to be steadily declining. The latest survey of British Social Attitudes (18th report, National Centre for Social Research) asked some questions about political engagement and trust, mainly to explore why apathy has reached such depths as were registered by the deplorable turnout at the last election. The verdict does not look good for a genuine tax debate.   In some ways, the British prove to be less apathetic than is commonly assumed. The survey, which is more meticulous than any opinion poll, produces figures that could persuade one there's plenty of life in the democratic dog yet. Though turnout is low, and interest in parliament in decline, engagement with public issues by other means is on the rise. Petition-signing, media-contacting, street protesting and even writing to an MP have grown markedly in the last 15 years. Many millions of us evidently still care about things beyond our precious lifestyles.   But to enlist us in a serious debate about higher taxation is to presume a reasonable level of trust in politicians to spend the proceeds well, and such trust seems to be in tatters. This is the only conclusion to draw from a wider measurement of confidence that was tested in a question asking whether people trusted British governments of any persuasion to place the needs of the nation above the interests of their own political party. Only 16% said they did so "just about always" or "most of the time". This is less than half the percentage (39) that said the same in 1974. The trust gauge steadily declined over three decades, with an upward blip to 29 in 1998, followed by the present abysmal figure, which implies a near halving of trust over the life thus far of the Blair government.   Whatever ministers say, in other words, the voters are becoming ever less inclined to believe in their selfless concern for the national interest. In particular, one may reasonably infer, if they say they want more of voters' money, they will face deep mistrust about how the proceeds will be used. Actually, another survey in a different context showed that, if asked the right way, people say they're willing to pay higher tax, including income tax. Last year's Fabian Society commission of inquiry into tax came up with old-fashioned, even socialistic, answers. But they were conditional on the belief that ministers can be trusted to give consumers of public services a better deal. An earmarked tax-rise for the NHS got 80% support.   Public desperation is already changing the context. Anxiety levels about health and transport in particular have now reached new peaks. Slowly but inexorably, the inviolable sanctity of the NHS as presently conceived is being challenged by intolerable waiting-lists and death-rates few other European countries suffer. The need for private money, essentially from the users of the service, subject to every kind of necessary means test, will become more glaring. Equally, the railway system cannot survive without public-private partnerships, organised on a basis that corrects the biggest scandal of the Major government, its rush to privatise at whatever price as long as the ideological pledge was met.   So the voters are ready for reform. They want to see investment and delivery on a level France and Germany regard as routine. Some of this will be with private money. But they're also ready for more public investment. What they await is a government that can break through the familiar contradiction, found in every survey on the subject, which reveals most respondents wanting better services and lower taxes at the same time, the Gordian knot that Gordon now seeks help in cutting. The apparent challenge is to his arithmetic. But the real one is to his credibility. How can he persuade the country that their taxes really are worth paying?   For in a sense, the debate is already over. Better services, in these elementary parts of civilised life, have now become such a paramount need that they've transcended the pressure for lower tax. We are a European not an American society, and demand the outcomes, if not always the methods, of social democracy. The demonstration effect of five years' Labour government has been, ironically, to prove the urgency of that priority by failing to deliver it.   What we know about political alienation is that much the greatest withdrawal of trust is due to the breaking of promises and the failure of delivery. Most other things, as the BSA survey suggests, are chaff in the media wind. So Gordon's discussion of forbidden subjects may be interesting. But not as a mask for what politicians should be doing, and are widely seen not to have done.