It was, unquestionably, a terrific Budget for Switzerland. The decision to raise the top rate of tax to 50 per cent will punish some bankers, but will simply send others scurrying to Geneva.

The vast majority of the 350,000 people earning more than £150,000 will, of course, stay in the UK. They will not complain. They will call their accountants. A higher rate of tax is likely to generate much less revenue than the Treasury hopes, and much more avoidance. But Mr Darling is also guilty of tax avoidance. His Budget sidestepped the central issue of the public finances: it answered the problem of future spending with a commitment to future borrowing but no clear or plausible route map to reducing debt.

As Chancellor, Gordon Brown said that public sector net debt would not rise above 40 per cent of GDP. Now that figure is projected to be 79 per cent in 2013-14. Such an extraordinary departure from its own rules surely required from the Government a sober account of the consequences.

What were we presented with instead? First, an entirely optimistic forecast of future economic growth. In years to come the best-remembered feature of this Budget may be its reliance on implausibly hopeful assumptions about future tax revenues. When these assumptions are revised, as they will surely have to be, they will reveal the need for far more strenuous efforts to curb public spending.

Second, there was an attempt to suggest that some relatively minor efficiency savings could do a job that needs to be done by serious reform of public service provision. Indeed, many new state schemes managed to be both expensive and footling at the same time, and seemed a greater preoccupation for the Chancellor than serious measures to reduce debt. There will be an extra £260 million for training in sectors that will have strong future demand, and a £750 million fund to support emerging technologies - as if the Treasury knows what these are. These schemes alone match the £1 billion in extra revenues assumed from the closing of tax avoidance loopholes.

Mr Darling did not explain how the Government will ultimately reduce borrowing, on the ground that only when the economy is growing will the Treasury be able to see how best to expand its revenues. He felt no such compunction about telling the well-off where they will hurt.

The political centrepiece of the Budget was a series of measures that sharply increase taxes on high earners. That this had a frivolous aim - to discomfort the Conservatives - does not rob it of a serious impact. It is a declaration of economic and political war on the country's entrepreneurial class.

In successive elections Tony Blair appeared to understand that social justice and prosperity for all were possible without penalising the better- off. Before the 1997 election he promised not to increase the top rate of tax. This solemn pledge, plastered on billboards all over the country, was renewed before the 2001 and 2005 elections.

Now it has been broken. The Chancellor has not simply increased the top rate to 50 per cent, he also moved the starting date to within this Parliament in direct breach of a central manifesto pledge. As the birth of this pledge was symbolic, so is its death. With it dies Mr Blair's political project. Labour is once again the party of massive public debt, inadequately controlled public spending and taxes on the wealthy.

In the past year we tumbled into recession, bailed out the banks and funded a fiscal stimulus. Yesterday we looked to the Chancellor to say how it would be paid for. The orchestra assembled. The audience settled expectantly. The conductor tapped his baton on his music stand. A hush fell. And from the stage came the shrill, thin sound of a penny whistle.