Leading article: A rash promise returns to haunt Mr Cameron

David Cameron promised that one of his first acts as Conservative leader would be to withdraw the party's MEPs from the centre-right European People's Party bloc in the European Parliament. It was an undertaking given early in his leadership campaign, when victory was far from certain, and it bought him the support of some of the party's stalwart Eurosceptics. A promise that may have seemed cost-free at the time, however, is turning out to have a price.

Conservative MEPs in Brussels are now split. Some are even threatening to leave the Conservative Party rather than leave the EPP. Their withdrawal, they argue, would weaken the Conservatives' representation in Europe and force them to line up with less savoury manifestations of the European right. There are suggestions, too, that the issue is dividing Mr Cameron from the shadow Foreign Secretary. William Hague, an undoubted ornament to the Tory front benches, has hinted that he might prefer his leader's promise to be placed on indefinite hold.

The mere suggestion that this might happen has raised the hackles of those at Westminster who gave Mr Cameron their support on the single issue of Europe. Thanks to one incautious promise, Mr Cameron now risks reopening all his party's old divisions over Europe, before he has even begun any real policy-making of his own. His working groups on other policy areas still have many months of work ahead before they are due to report.

Worse, if it were possible, Mr Cameron's handling of the Europe issue is starting to raise questions about his judgement. When candidate for leader, Mr Cameron apparently failed to see how such an apparently minor procedural issue had the potential to grow into something else. By the time he did see it - or it was brought to his attention - his options were to reverse track and seem fickle or stick to his guns and store up trouble for later. Without other policies on which to show his mettle, this is an unenviable choice.

With hindsight, and in the knowledge of how safe a majority he eventually won, it is unfortunate that Mr Cameron allowed himself to be trapped on Europe in this way. Unfortunate for him, too, that the EU Constitution - the issue on which he decided to split from the EPP - is no longer pressing. EU leaders have just kicked it into touch until 2009. In this sense, Mr Cameron picked a quarrel he did not need to have.

He is now said to have given Mr Hague until the end of this European Parliament session to effect the Conservative MEPs' withdrawal. This may be one of those rare times when a good old-fashioned EU-style fudge looks like the best option on offer.