Shadow Trade and Industry Secretary John Redwood said Tony Blair was "ashamed of his policy to abolish the pound".

The Tory leader on Thursday challenged Mr Blair to a debate on the single currency and sterling.

The prime minister has said his government will only take the UK into the single currency when it believes it is in the national interest, if the move is approved by a referendum.

Speaking on Friday, the prime minister insisted the drop in the fledgling currency's value had not altered this stance.

"Our position remains exactly the same and I don't think you can judge it on the basis of fluctuations of the euro from this month to that," he said.

He accused the Conservatives of trying to talk the currency into collapse.

"If the euro fails, Britain will feel the results of that," he said. "It's in our interests that it succeeds."

William Hague: "Blair wants to scrap the pound"

But Mr Hague told a party rally in Plymouth, Devon, that Mr Blair was avoiding the issue.

"There is no European issue that Labour wants to talk about less than the single currency," he said.

"Tony Blair wants to scrap the pound. He knows that British people do not want to scrap the pound - so he wants to change the subject."

A Daily Telegraph poll on Friday suggested public support for the euro had fallen. Only 29% of those surveyed said they wanted the UK to join the single currency, compared to 34% six months ago.

'Any time, any place, anywhere'

On the day the euro slid to another record low, Mr Hague told Tory Party members Mr Blair refused to debate with him during the European elections.

"Today I challenge him again. I challenge him specifically to a debate on the single currency and the pound. I want that debate before next Thursday. But if Mr Blair won't agree to that then I will debate with Mr Blair after polling day or any day.

"Any time, any place, anywhere, Mr Blair," said Mr Hague.

The Conservative leader said the UK had the fifth-largest economy in the world - "and we can make a success of our own currency and economy if we wish to do so".