Unguarded comments by European Commission president Mr Romano Prodi about the irrevocability of euro membership have once again landed him in controversy.

Yesterday his spokesman, Mr Jonathan Faull, struggled, with only a modicum of success, to explain to a deeply sceptical press that, when Mr Prodi told a British MEP that it might be possible for states once in the euro to opt out and yet still remain in the EU, he had, in fact been talking in strictly hypothetical terms.

What Mr Prodi did not realise was that the Tory MEP, Mr Daniel Hannan, who had asked to meet him privately in that capacity, is a former Daily Telegraph journalist and was actually taping their discussion not for private reference but with a view to writing up an interview for the Spectator. Mr Hannan's ethics have left the British press corps troubled.

The treaty governing the euro is unequivocal. It refers explicitly to the "irrevocable fixing of exchange rates leading to the introduction of the single currency".

But the Danish Prime Minister, Mr Poul Nyrup Rasmussen, suggested recently during his country's bitter referendum campaign on joining that Denmark could leave and reintroduce its own currency if it found the euro experience uncomfortable.

Mr Prodi was drawn into the controversy recently in Denmark and answered at first with a flat denial and then, concerned not to expose Mr Rasmussen, with a comment not unlike that which got him into trouble with Mr Hannan.

When quizzed by Mr Hannan last week he is reported to have hesitated and then responded: "What I have to say is that there is no provision in the treaty for withdrawal. This is stating the obvious. But of course in an extreme case, one could always foresee, for example, that Texas might leave the dollar. But this is not strictly in the US Constitution."

Pressed again on the possibility, he added: "If there were exceptional circumstances and provided it was not done in a way which was hostile to the European Union. It is impossible to foresee for certain."

And still remain in the EU, Mr Hannan persisted? "Certainly it's possible. There are countries today which are full members of the EU but are outside the euro," said Mr Prodi, digging himself deeper into trouble

By yesterday, Mr Prodi's comments were causing his spokesman no end of difficulty. The euro would be a great success, he said; it was inconceivable anyone would want to leave.

"Something may be theoretically possible in circumstances which no intelligence on this earth can foresee today," Mr Faull bravely told the Commission's daily briefing. "Yet, in the realms of the real economy and real politics of today, I'm telling you that it is inconceivable that a member-state which is part of the European Economic and Monetary Union would or could leave it." He said it was legally impossible, and politically inconceivable. "It would be quite wrong, and that is where the President's remarks have been taken out of context, to . . . suggest a member-state can enter the euro and leave it more or less at will," he said.

Did the President regret his comments? No, only their misinterpretation, said Mr Faull, now surely economising with the truth.