An NOP survey for the Independent finds that public opinion has shifted in favour of euro membership.

Asked how they would vote if the government's economic tests were met, 41 per cent were opposed to joining the euro, 37 per cent were in favour, 17 per cent said they wouldn't vote and six per cent didn't know.

An aide to Tony Blair told the paper the poll was "very encouraging".

The findings come after the government was told that a pro-euro stance could cost it 100 seats at the next election. The warning came from a new campaign group, Labour Against the Euro, yesterday.