Mr Mandelson is better than his detractors admit, but he will be bad news for Europe

He stabs his political foes in the front far more often than in the back - those with whom he quarrels learn about it from him

Tony Blair does have a conscience. Three years ago, when Peter Mandelson got into difficulties over the Hinduja brothers, the PM panicked, as did Alastair Campbell. They assumed that Peter must have done something seriously wrong. Mr Mandelson was so crushed by this vote of no confidence from close friends that he made no attempt to fight back, but merely drafted a resignation letter which was saturated in self-pity.

It quickly became clear that there had been no wrongdoing. Since then, the Prime Minister has been determined to compensate his old friend: hence the latest appointment.

But Mr Blair does not control his own Government, or its plans for the third term. He had identified a major weakness, at the Department of Work and Pensions. The present minister is Andrew Smith. Who? You may well ask. It would be charitable to describe Mr Smith as a nonentity. He has been in Parliament for 17 years without ever saying or doing anything of any interest. He has spent his years as a minister reading out departmental briefs in a dull monotone, as if determined to convince his listeners that he was merely the messenger and had nothing to do with the strategy. Not that they needed convincing. Even by the standards of this Government, Andrew Smith deserves a place in the record book. This is a minister who has never shown any desire to think for himself.

Now that Mr Blair wants to address the problem of welfare - though we have heard that before - it is natural that he should start by sacking Mr Smith and replacing him with Mr Mandelson: the mediocrat giving way to the mediacrat. But it could not be done. The PM was confronted by sustained opposition from senior ministers. As a result, Mr Mandelson is off to Brussels while Mr Smith has a little longer in office to give obscurity a bad name.

Mr Blair once said that one of his long-term objectives was to persuade the Labour Party to love Mr Mandelson. There were echoes of Winston Smith in 1984, who learned to love Big Brother. Fortunately for the Labour Party, the methods used to induce him to do so are not - yet - available to Mr Blair, which may be why the experiment has failed. Instead of loving, much of the Labour Party loathes.

This too is unfair to Mr Mandelson. In the first place, he is not nearly as devious as his reputation suggests. There was the unfortunate affair of the mortgage application, but he stabs his political foes in the front far more often than in the back. In most cases, journalists and Labour politicians with whom he quarrels learn all about it from him, face to face.

Even Gordon Brown has far less to complain of than he would like to think. In the late Eighties, Mr Mandelson assumed that Mr Brown was the pre-eminent figure in his Labour generation. In those days, so did Mr Blair. Mr Brown was happy to concur. But after 1992, things went wrong. Mr Brown's reputation failed to progress. As shadow Chancellor, he did not use his opportunities nearly as effectively as the shadow Home Secretary was doing: one Tony Blair.

After John Smith's death, when Mr Mandelson switched his allegiance, he wrote Mr Brown a long letter in an attempt to soothe the pain. It spectacularly failed to do so. No doubt parts of it were insincere, but would Mr Brown have preferred a truthful letter? That would have been much shorter, for it would have read as follows: "You are not as good with the media as Tony is. You are not as marketable to swing voters. You are not as electable, and you are a difficult cuss. So I'm going with Tony."

In changing sides, Mr Mandelson was no more guilty of deviousness than Mr Blair was, but there is the rub. Even Mr Brown would find it difficult to accuse his Prime Minister of deviousness for 24 hours a day, so he often vents his feelings on Mr Mandelson. The same is true of many Labour MPs. They are reluctant to face the reality that Mr Blair has deliberately set out to transform the Labour Party into an entirely different political creature, while denying its members - or its MPs any say in the process. At least until recently, most dissident Labour MPs preferred to blame everything on Mandy rather than oppose Mr Blair. They were wrong. Whatever vivisection Mr Mandelson committed on the old Labour Party had Mr Blair's enthusiastic backing.

Mr Mandelson will now be operating in an entirely different political environment where the skills and authoritarian reflexes which he has developed in British politics will not be relevant. The European Commission functions as a collegiate body. Its individual members are expected to renounce their national allegiances and to work together for the common European good.

This, of course, is a gospel of perfection. No one expects a group of people who were appointed because they had been politicians to forget everything about their past politics. But there are limits, as Romano Prodi discovered. One reason why his Presidency is so universally regarded as a failure was his inability to distance himself from Italian politics. The sense that he was using Brussels as a base from which to plot his return to a frontline role in his native country did him lasting damage.

Mr Mandelson will have to be careful. But he has proved that he can function in different political environments, for he was an effective Northern Ireland secretary, a job which cannot be done by treating the local politicians as if they were Labour backbenchers cowering under the threat of de-selection. There is no reason why Mr Mandelson should not be an effective commissioner.

Not that Mr Blair has sent him to Brussels in order to detach him from British politics. He hopes that Mr Mandelson will help him to achieve the same miraculous cure for British Euroscepticism as the two of them did for the old Labour Party's disorders. In the PM's view, the team which made Labour electable can do anything.

In this, Mr Blair is overlooking some crucial factors. One reason why Labour became electable in 1997 was the British public's contempt for the Tory party. These days, many British voters have as much enthusiasm for the European Union as they used to have for the Major government. Mr Mandelson may be a formidable spin-doctor, but the British distrust of Europe cannot be spun away - especially as so many voters also distrust Mr Mandelson.

This is likely to be exacerbated by the vulgar press. In Brussels, Mr Mandelson will achieve something which has eluded his predecessors. He will make the European Commission newsworthy. But it is unlikely to be good news. The impression will be given that Mr Mandelson is enjoying an exotic social life, paid for by the British public, while hatching plots to impose even more burdens on Britain. Mr Blair may believe that his old friend can work magic on British opinion. Despite recent successes at Westminster, this is further evidence that Mr Blair himself is losing his own feel for public opinion.