The row over membership of the euro-x club - the informal group of EU finance ministers who will discuss policy after the creation of a single currency - is deepening.

Attempts to solve the row this week collapsed, with even a few Byzantine suggestions from the EU Commission failing to break the deadlock.

The crux of the problem is that the countries joining the single currency believe they should be the only members of the new council, while the outsiders argue that they should also have a voice.

The dispute may appear trivial. After all, the council will not have any formal power. But it is a symptom of something more fundamental, which is the difficulties the EU will face in managing relationships between those inside the single currency and those outside.

The EU already, of course, has some member-states moving ahead of others; for example there is free movement of people across much of Continental Europe under the Schengen agreement, to which Britain and Ireland have not signed up.

But monetary union is the most far-reaching step in the field of economic co-operation that the EU has taken.

If the EU is to remain cohesive after the introduction of the single currency, then those outside the club must not be seen as "second-class" members. A lot of difficult talks on this subject lie ahead and it could yet blow up into a major row early next year, when the time comes to choose who will be inside the euro club and who will stay out.