Suddenly, every politician wants to be bold. But where has it got them?

Margaret Thatcher is to blame. From early on in her leadership she proclaimed her boldness at every available opportunity. By the end of her premiership it was more important for her to be bold than to be right.

This superficially alluring adjective "bold" has mesmerised political leaders ever since. John Major boldly out-Thatchered his predecessor by privatising the railways. Iain Duncan Smith seeks to show he is boldly in command by sacking those who dare to disagree with him. Tony Blair declared at his party conference last autumn that his government was "at its best when at its boldest".

The problem is that boldness is not a policy in itself. It is not even an adequate way of defining an approach to policy. Some have praised the Prime Minister's approach to Iraq as "bold" when surely the key question is whether he is right or not. In this newspaper today Mr Blair responds to a range of readers' concerns about his approach to Iraq. If you agree with his responses you will probably conclude that he is also being bold. If you disagree, you will quickly reach the judgement that it is not necessarily bold to share the same point of view as the world's only superpower, backed by most of the right-wing bullies in the press.

That is another problem with boldness. The term is deeply subjective. I am keen for Britain to join the euro. If Mr Blair were to hold a referendum I would no doubt celebrate his boldness. But what if he were to lose the referendum or join the euro at the wrong exchange rate? Then he would have been boldly misguided.

Proclamations of boldness are no more than imprecise slogans, an extremely dangerous political tool. Ask John Major, who in one of his relaunches declared that his government was going "back to basics". The problem with "back to basics" was not that half of Mr Major's party, including him, had had or were having affairs of one kind or another. The problem was the imprecision of the slogan. What exactly did it mean? Some of his aides took it to be an attack on sexual permissiveness.

Mr Blair's pledge that his government was at it best when at its boldest is in danger of becoming his "back to basics". While his attention and that of his senior circle are on the war, some of his aides have seen the "bold" slogan as the green light for muddled thinking on the future of public services. More broadly, they have seen it as a signal to knife the Chancellor. As a result, these eager Blairite outriders – I christen them the "boldists" – are setting up a possibly fatal and partially unnecessary divide between Mr Blair and Mr Brown.

Here is the broad scenario conjured up by leading boldists: the Iraq war is over quickly, and a triumphant Prime Minister is emboldened to sack the Chancellor as part of a modernising reshuffle. There is no doubt that this is an event that some boldists dream of: theyfantasise about it, promote it to selected journalists.

There is a fatal flaw in their fantasy. The boldists misread the growing concerns about the war within the Labour Party. Nearly all those MPs who voted against the Government last week expect a short war. Their objections are about the consequences of war, humanitarian and political. Mr Blair will be a hero to those right wing commentators who have supported him all along, but he will not be a greatly strengthened figure in his own party even if the military conflict is brief. I would be surprised if he is in a strong enough position to sack his Chancellor. I would be equally surprised if he was inclined to do so. He would know that, having soaked up gallons of goodwill over Iraq, it would be time for rebuilding his party rather than destroying it altogether.

More ominous are the briefings from the boldists on policy. Governments can survive personality differences. They become much more fragile when there are policy splits. On the NHS the boldists like to portray themselves as crusading modernisers and Mr Brown as an old Labour control freak.

This is why I wrote earlier that the divide is partially contrived. Here are some facts. They are so rarely aired I could almost claim to be offering sensational exclusives. Mr Brown is not an opponent of foundation hospitals. He is even less an opponent of allowing all hospitals to have foundation status. He believes that if they were all given the freedom to innovate, there would be much less danger of a two-tier system. The Chancellor has remained adamant on a single issue – that foundation hospitals should not have powers to borrow in such a way that their only means of repaying the loans would be by expanding private health care and charging patients.

On this point he is right to be adamant. The Government's main objective at the moment should be to expand NHS capacity, not to offer more incentives to build up the private sector. This is not about Treasury control freakery. It is about preventing hospitals heading in the same direction as dental practices, where patients are told that if they want a quick appointment and better treatment they should pay for it out of their own pockets.

Perhaps this is what the Blairite boldists envisage. It may even be what Mr Blair envisages. In an extraordinary article for the magazine Progressive Politics he writes of the need to "experiment with new forms of co-payment in the public sector". Possibly the Prime Minister is referring only to top-up fees for universities, but if he is applying the principle to the NHS and schools he is toying with ideas rejected by the Thatcherite no turning back group in the 1980s, on the grounds that they were unworkable. NHS vouchers, topped up by payments for those lucky enough to have the cash, would be boldly impractical as well as being boldly incoherent. It would mean the end of the NHS at a time when Mr Blair often proclaims his support for it.

This is why the briefings of the boldists are, apart from anything else, bad politics. In a few weeks' time taxes are going up to pay for improvements in the NHS. This is not a moment to imply that the NHS needs breaking up. The Shadow chancellor, Michael Howard, has started to quote the Secretary of State for Health, Alan Milburn, in defence of Conservative claims that the NHS is not working and that therefore the tax increases are a waste of money. There will be much more of this from the Conservatives. Mr Howard is on to something.

In more ways than one the reckless boldists should move on from the 1980s. It is much more important to be right than to be bold.