Wealth by stealth is Treasury's secret weapon

Gordon Brown's great trick when he came to power in 1997 was to put up taxes when he did not have to. It meant that for the rest of the Parliament he was ahead of the game, always with more money than he needed, always delivering better-than-expected results and always leaving himself room to manoeuvre should something unexpected come along. It allowed him to appear in control and gave substance to his claim that the economy was in safe hands.

The core of today's Budget is that he is trying to repeat the trick for the second term. Of course, five years ago no one realised that taxes were being raised, hence the well-justified stealth taxes sobriquet which is underlined in today's Budget documents which show that the total of tax paid today is £60 billion a year more in real terms and almost £100 billion a year in actual pounds than it was when Labour came to power.

That is an increase of more than a third and is the key to Mr Brown's seemingly effortless ability to cope with the vicissitudes of the world economy or domestic politics.This time round there is no need for stealth and it must be said no opportunity as all the secret pots have already been plundered.

He says that compared to last autumn, world economic prospects are much brighter. And as we all know domestically the political mood has changed enough to allow the Government to talk openly about the need for tax increases to fund improved public services.

This openness is hailed as the end of spin, which is itself a great irony because it is in fact one of spin's finer achievements. The tax debate has been all about how the money will be raised - an increase in National Insurance - and what section of society will be hardest hit - those earning about£30,000 a year. It has not at all been about whether the money is needed, nor whether taxation is the best way. The Chancellor has avoided any detailed examination of how in fact the money will be spent. Though you would never guess it from the speech, the key to how much more money flows into the Exchequer is not how much we pay in income tax or NI, but the rate of economic growth.

Growth is good because it means people are employed and paying tax rather than unemployed and receiving benefit. From the Chancellor's standpoint it is doubly good because it means the overall cake is bigger.

If the economy expands by 2 per cent this year it means the nation's wealth will have gone up by £20 billion in 12 months and the tax take on that is £8 billion - which is of course more than the £7 billion we were told he had to raise by higher taxes.

If growth is faster still, as his confident tone implies, the covert windfall is proportionately greater.

Last time Mr Brown created his comfortable cash buffer by doing all his sums as if he was poorer than he actually is and keeping quiet about the windfall.

He did it again today. Unless the economy really takes a turn for the worse, which he clearly thinks will not happen, he will almost certainly rake in billions more than he says he will.

Today's tax increases are driven by what seems politically acceptable but they also make good economic sense.

It was obvious from his speech today that the main threat to our prosperity is the domestic one - that the high street shopping and housing boom will spiral out of control and force the Bank of England to put up interest rates.

This will slow growth and carries the added political risk that a lot of those voters who have borrowed heavily will find it a struggle to pay the higher charges.

By taking in more tax than he needs to cover present spending commitments, Mr Brown is helping to damp down spending and blow the froth off the boom.

Though he would not admit that is his intention, it will be a huge help to the Bank of England as it struggles to keep interest rates down.

And that is why the verdict on this Budget should be that, as far as the big picture is concerned, Mr Brown is trying to do good by stealth.