In an interview with the Guardian, Tommaso Padoa-Schioppa, a member of the executive board of the European central bank and the man widely credited as the intellectual impetus behind the euro, said Britain's inclusion in "euroland" would destabilise the euro unless there was a fundamental shift in British attitudes towards Europe.

"In most European countries a shift in politics does not fundamentally change the country's European policy," he said.

"But there are some countries, like the UK, where the fundamental attitude of the population is not united behind the EU. So long as they are not members of euroland this fragility of support does not worry me. I would be concerned if this fragility remained and they were part of euroland."

His comments came as the Liberal Democrat leader, Charles Kennedy, last night accused Tony Blair of running away from a decision on whether Britain should join the euro and called on him to openly state his policy.

But, according to Mr Padoa-Schioppa, even if a Labour government were to win a referendum on joining the single currency, it would still need to win over the hearts and minds of the vast majority of the electorate before it could comfortably take its place at the heart of Europe's economy.

In countries on the continent a change in government would not signal a meaningful change in policy where European integration was concerned, he said. In Britain, however, there were significant differences not only between parties but within them.

He said the euro's long term credibility had not necessarily been damaged by its low value: "The real sign of success, or lack of success, is that the euro is accepted as a reality ... that it is here to stay."