Opponents of British entry into the European single currency last night welcomed Sweden's rejection of the euro.

The referendum to adopt the euro has failed, announced Prime Minister Goeran Persson.

Earlier, exit polls indicated that Swedes had voted to keep the kronor by a narrow margin of 51.8 per cent to 46.2 per cent.

The poll took place under the shadow of the murder of fervent europhile Foreign Minister Anna Lindh.

Sweden was one of only three EU nations not to adopt the euro at its launch, and observers had suggested that a Yes vote would add to the pressure on Britain to join.

But supporters of British entry insisted that a No vote in Sweden should not be allowed to delay the calling of a referendum in the UK.

George Eustice, director of the No campaign against British entry, said: "The early indications from Sweden highlight the huge difficulty that the Government would have winning a vote in Britain, where opposition is even higher.

"People in Sweden have seen the serious problems in the eurozone and they are concerned about giving up control of their own economy and compromising public sector investment."

Labour backbencher Chris Bryant, chair of the Labour Movement for Europe, said: "Obviously I would have preferred it if Sweden had voted Yes, but Sweden is Sweden and Britain is Britain and we have a very different economy.

"Many of Sweden's trading partners are not in the euro or even the EU, like Norway, whereas with Britain, more than half of our trade is with euro countries.

"I hope that Britain will be joining the euro as soon as possible, so that we reap the benefits of increased trade and don't risk economic isolation."

Mr Bryant welcomed the result of a separate referendum in Estonia, where voters opted to join the EU by a two-thirds majority.

"My guess is that in two or three years' time, they will want to join the euro as well," he said. "We have to make sure that when Estonia, Poland and Hungary have a seat at the table deciding Europe's economic future, Britain isn't left out."

Europhile Cabinet minister Peter Hain, speaking before polling stations closed in Sweden, said that the timing of a UK vote would not be affected by the Swedish result.

"Just as the Swedes are making their own decision about the euro today, so we will make our own decision in Britain's interests in the right economic circumstances," he said.