A majority of the public would vote against the EU constitution in any referendum, according to a new poll.

The YouGov survey in the Telegraph suggests that 51 per cent would vote "no" while just 23 per cent would say "yes".  A further 21 per cent are in the "don't know" camp.

Indicating that winning a referendum could prove difficult for the government, just 36 per cent of those polled think that EU membership is "a good thing".

However, Tony Blair today steps up the campaign for the treaty, saying that the enlarged EU will prove beneficial for Britain.

Writing in the Times, he says that "the new members will help us to ensure Europe is ready to meet the difficult challenges of the future".