EU Commissioner Chris Patten has warned Britain risks excluding itself from the EU if the public votes no in the forthcoming constitution referendum.
Chris Patten wants closer EU-UK integration
The former Tory minister made the comment as the News of the World released survey findings suggesting only 25% of Britons would vote yes.
It also suggested 51% thought Britain would stay in the EU anyway, regardless of a no vote in the referendum.
The Sunday Times claims Tony Blair has admitted his EU U-turn "backfired".
It says the prime minister has told senior aides he "regrets" his decision to allow a referendum amid speculation he will leave office if the British public votes to accept or reject the EU constitution.
Another ICM survey, commissioned by the New Frontiers Foundation, suggested only 21% of the British public would back the proposed EU treaty in a vote.
Commenting on the poll, shadow foreign secretary Michael Ancram said Britain's interests were best served by saying yes to Europe but no to handing over more control to the EU.
Mr Ancram said he believed the constitution would mean a hand-over of power from Britain to the EU.
"This poll shows that the British people understand this and they will not be fooled by a government that tries to twist the debate and scare them into thinking they would be forced to leave the EU if they voted no," he said.
In or out?
Mr Patten told the Observer newspaper that Britain had to make its mind up whether it wants to make a success of Europe or not.
He said: "That's why I think that, if we ever get to this referendum, it's really going to be about whether we want to stay in.
"What's the point of being inside and endlessly, truculently making trouble? Is that really pursuing the national interest?"
A Downing Street spokesman said the ICM figures were to be expected as the debate had not begun yet.
"We do not have a final constitution, but once people understand the reality of what is agreed, that is where a referendum can be won," he said.