Europe minister Peter Hain has dismissed the idea of running the euro as a "parallel" currency alongside sterling.

With the euro's first business day judged to be broadly successful, European Commission officials described themselves as "extremely satisfied" with the change over.

And with the logistical operation running smoothly, the euro rose strongly on the foreign exchange markets on Wednesday, with its biggest one day rise against sterling.

The success prompted renewed debate over the implications of the euro for Britain on Wednesday, with Conservatives accusing the government of seeking to portray membership as inevitable.

Hain told BBC radio that it would be unlikely that Britain could use the euro in parallel with sterling. "As for the idea that we can have it both ways, we will asses that over the next 15 months," he said. "I doubt in the end that it is possible to run a sort of parallel currency economy."

Hain also hinted that chancellor Gordon Brown could complete his analysis of whether membership met the government's five economic tests earlier than expected, saying it wasn't likely to be left to the last possible date, midnight on June 6 2003.

But Conservative Party chairman David Davis said the government did not have a strong case for joining the euro. "The fact that they are trying to ride the argument of inevitability demonstrates actually how weak their case is, that there aren't any stronger arguments," he said.

European Commission president Romano Prodi said the introduction of euro notes and coins was a "special day" for Europe. He also called for more rules to coordinate economic and budgetary policies, saying "This is not something that will happen overnight but it is an inevitable process".

The tabloids have mixed success in their first experience of the new currency. The Mirror claims to have spent the first euros in Britain yesterday, buying a coffee and croissant at Heathrow airport with helpful staff converting pounds to euros. The Sun says its reporters found themselves paying higher charges when using the euro to purchase a variety of goods from British shops.