Some members of William Hague's Shadow Cabinet believe the Tories should not abandon their opposition to the euro even if Tony Blair persuades the public to accept it. He is expected to call a referendum shortly after the next general election if Labour retains power.
Michael Howard, the Shadow Foreign Secretary and a Eurosceptic, is among senior Tories who believe Mr Blair may try to "bounce" the British people into joining the euro without giving them the chance to see whether it works.
Mr Howard thinks it may be possible to persuade the public at a later date that Britain was wrong to enter the single currency and does not accept the move would be irreversible. Although it would he harder to pull out of the euro than the Exchange Rate Mechanism, from which Britain was forced out in 1992, he believes that a determined member state would be allowed by the the EU to quit.
Although some sceptics agree that the Tories should "not throw in the towel" after losing a referendum, other hardliners fear they would alienate the voters by refusing to end its opposition to the euro. "Fighting on would just prolong the party's agony over Europe," said one sceptic. " But there is already a debate about what we should do if Blair wins a referendum. We will have an acute dilemma."
Francis Maude, the Shadow Chancellor, believes the Tories should accept the referendum verdict. He told the Tory conference on Wednesday: "The single currency is not just for Christmas - it is forever."
Mr Hague is also said to be a pragmatist on the issue. "We would be crazy to tell the British people they had got it wrong," said one aide.
Amid further Shadow Cabinet tensions, it emerged last night that Mr Hague had slapped down Mr Maude for saying the Tories offer the option of taking Britain into the euro in "seven or eight years". This puts a more positive gloss on the party's policy of ruling out membership in this Parliament and the next.
Mr Hague tracked down his Shadow Chancellor in Portugal last week to order him to stick to the official line. Although Tory officials insist there is no split between the two men, they admit privately there is "a difference of emphasis" in the way they portray the policy.
One source said: "Francis Maude does not want to be locked into a bald statement that we will not join, so he gives the other side of the same coin and says we might join after the election after next."
Mr Maude is anxious to reassure British businessmen, many of whom support the single currency, that the Tories are not opposed to it in principle. There are fears that big companies will stop giving money to the Tories because of Mr Hague's hardline stance.Reuse content