Pressure on the Tories to offer a referendum on the EU's Lisbon Treaty has intensified when a poll found 70% of voters want one even if it has already become law.
Opposition leader David Cameron insisted this week that he was determined to press ahead with plans for a referendum even if the Irish vote to accept it next month.
But the party has repeatedly refused to spell out what they would do if the treaty had been fully ratified by the time they came to power, simply saying that they would "not let matters rest".
Desire for a referendum no matter what was also strong among Labour-leaning voters, the ICM poll for the Sunday Telegraph showed, with 64% wanting the Tories to go to the country if elected.
The survey also found 40% wanted Britain to be pulled out of the European Union altogether, up on other recent surveys.
One in 10 thought Britain did best out of its membership, with 43% naming France and 25% Germany.
Mr Cameron said a Conservative government would put the treaty to a popular vote in Britain as long as it had not been fully ratified by all the EU member states.
Even if the Irish did reverse last year's "no" vote in their second referendum on the treaty - which takes place on October 2 - Poland and the Czech Republic are yet to fully ratify the treaty.
"Unless and until they do that, the Conservative Party will be absolutely clear that we want to have that referendum, we want to recommend a 'no' vote in that referendum, we want to withdraw the British articles of ratification as a result of a 'no' vote in that referendum and change Europe in that way," Mr Cameron said.
Ireland is the only EU member state to have held a referendum on the treaty - although the French and Dutch have previously voted to reject the earlier EU constitution, which critics say is virtually the same as the treaty.
