We exclude him from the bosom of our Holy Mother the Church in Heaven and on earth, we declare him excommunicated and anathematized and we judge him condemned to eternal fire with Satan and his angels and all the reprobate.’

So runs the ceremony of excommunication in the Catholic Church. Weirdly, the ever-secular left has something to learn from just such a definite and public ritual of expulsion. This is because of the sizable industry of former leftwingers who trade on their now defunct socialist credentials to make a living in the rightwing media.

Take Christopher Hitchens. Or Melanie Phillips. Or Georgia Democratic Senator Zell Miller. All have two things in common. First, they are barking rightwingers. Second, they are always introduced as people who are, or were previously, on the left. They are the darlings of the right because they are supposed to prove that people on the left are misguided – as though being left is a hormonal balance or a fever of youth. Actually, it is usually the other way round. These people move from an interval of lucidity to full-fledged membership of the brigade of rightwing sky pilots.

Take Zell Miller. As governor of Georgia, he introduced free state nurseries and free university tuition for Georgians who kept up a B-grade average. He even tried to get the confederate flag removed from Georgia’s own flag. So far, so not so barking. Then make your own mind up about his speech, as a Democratic senator, to the Republican convention:

‘Now, while young Americans are dying in the sands of Iraq and the mountains of Afghanistan, our nation is being torn apart and made weaker because of the Democrats’ manic obsession to bring down our Commander-in-Chief.’

This is loopy. Surely the president’s conduct of war in a democracy demands discussion, not immunity? And since when is an election a vicious attempt by a challenger to steal the incumbent’s job? Should Kerry simply have stood aside and not offered people an election this year?

Similarly, Christopher Hitchens’ decline from lefter-than-thou firebrand to George Bush’s unkept John the Baptist may not have been a straightforward shift into the realm of sense. From describing Bush as ‘abnormally unintelligent’, Hitchens has become his great supporter, and a great attacker of Kerry. He says:

‘I’m a single-issue person at present and the single issue, in case you are wondering, is the tenacious and unapologetic defence of civilised societies against the intensifying menace of clerical barbarism. If in the smallest doubt about this, I would suggest a vote for the re-election of George Bush, precisely because he himself isn’t prey to any doubt on the point.’

There is a terrible crabbedness to this coming out as a conservative. It was followed up in the same broadly liberal forum, Slate.com, by a series of down-the-line Republican attacks on Kerry. And this is the problem: these darlings of the right linger on the leftwing press, using all their residual prestige to conduct the work of their new masters.

Melanie Phillips’ biography on the BBC reads: ‘Styled a conservative by her opponents, she prefers to think of herself as defending authentic liberal values against the attempt to destroy western culture from within.’ Pilgrim might well prefer to think of himself as a toned love god, but sadly it just ain’t so.

But why is it so important anyway for Melanie Phillips to claim she isn’t a conservative, and to stress her time at the Guardian, when she so long ago made up her bed on the right? Why does Zell Miller not cross over to the Republicans? Why does Christopher Hitchens still haunt the leftwing media? Why can’t these people let go? Why have they still got one foot in the leftwing closet?

It serves the rightwing media to have these perpetual prodigals. They eternally relive the glorious moment when they crossed over the threshold. The apostates themselves get to cry out that they have not changed but the left has abandoned them.

It is time to put a stop to this half-life for former lefties. Cast them out! We must find a suitable pontiff of the left to excommunicate lefties who are on the turn. Watch out pundits and columnists everywhere. And then, when the anathema is pronounced, we cry out: ‘Fiat, fiat, fiat’. And then, ‘cast to the ground the lighted candles we have been carrying.’