Ministers have lined up to back government policy on the European single currency and dampen speculation that the introduction of euro notes and coins on the continent signalled inevitable UK membership.

Europe minister Peter Hain denied that he had been reprimanded by his boss, foreign secretary Jack Straw, over reported comments that euro membership was "inevitable" following the introduction of the single currency in 12 euro-zone countries on New Year's day.

And backing the government line he reiterated that the economic assessment for the UK joining the single currency would have to be "clear and unambiguous".

"I was told that I had said joining the Euro was inevitable. I've never said that. Nothing is inevitable in politics, there has got to be a referendum," he told GMTV.

Addressing the issue of whether the decision to join was a political question, rather than economic one, Hain said: "We are politicians, we are an elected government, the government will form a view on the basis of the economic assessment, so if you like it's a political judgment on the basis of an economic assessment."

Treasury chief secretary Andrew Smith also insisted that any assessment on euro membership would be made on "economic grounds".

"To short cut or to fudge the assessment and to join without making sure rigorously that the tests are met would not be in the national economic interest,'' he told the BBC.

"This government is determined that we will take the right long-term decisions for Britain so we won't rush the tests or fudge the assessment and we won't take any risks with Britain's hard-won economic stability."

And leading cabinet pro-European Robin Cook stressed the "fundamental" economic precondition that must back the government's approval of the euro in principle.

"The position is that we believe in principle that Britain could be better off inside the euro ... but the economic conditions have got to be right. That is not window dressing, that is fundamental," he told the BBC.

But the Commons leader also warned that the UK could find it increasingly difficult outside the euro-club - an important political consideration for a prime minister concerned about his international role.

"It is both political and economic and both those considerations have to be right. On the political side it is clear that we are gaining a lot from the leading role we have in Europe," he said. "If we want to continue with that very strong powerful leading role within the European Union it is going to be more challenging to do that if we are outside the inner club but the economic side has also got to be met."In an interview for the Sunday Times, Labour party chairman Charles Clarke hinted that 2002 would be a "decisive year for us" and that euro-membership was a "political imperative".

"It is a critical issue for the future of the country," he told the newspaper. "The fact of the euro notes and coins coming in on January 1 has been a most dramatic event and will be seen as increasingly dramatic as the years proceeds. This will be a decisive year for us in relation to these issues."