The move risks a backlash from pro-EU Tories, led by Kenneth Clarke, who had hoped that William Hague would play down the single currency issue during the campaign to avoid displaying the party's divisions on the issue.
Andrew Lansley, a Tory vice-chairman, said yesterday the euro would be a "significant factor" in the elections and the party would pursue vigorously its policy of ruling out British membership in this Parliament and the next.
"There are a significant number of people who may in other circumstances see themselves as Labour or Liberal Democrat voters, but who agree with Conservative policies on Europe and the single currency in particular," he told a press conference.
Mr Lansley dismissed the newly formed Pro Euro Conservative Party, led by the rebel former Tory Euro MPs John Stevens and Brendan Donnelly, as "a party of the disgruntled and disaffected". He said: "The number who vote for the Pro Euro Conservatives will be vanishingly small, compared with the numbers from other parties who will come to the Conservative Party."
The Pro Euro Tories, officially launched in London tomorrow, plan to contest every seat in every region of Britain at the election, putting up 84 candidates in all. They include Sir Anthony Meyer, the former Tory MP, whose "stalking horse" challenge to Margaret Thatcher in 1989 paved the way for Michael Heseltine to run for the leadership a year later, forcing her resignation.
The party's manifesto calls for early British membership of the single currency and argues that millions of voters would be deprived of a voice in the elections without it. Its leaders claim they could capture 10 per cent of the Tory vote.
"The extremism that underlies the Tory policy on Europe is alienating many Conservatives," said Mr Donnelly. He attacked Mr Hague's keynote speech on Thursday, calling for EU countries to have an opt-out from new EU laws.
Mr Donnelly said the speech was "a gigantic step" towards confirming his suspicions that Mr Hague would like Britain to pull out of Europe. Mr Stevens said: "It is obvious that William Hague is trying to raise the temperature in his anti- European rhetoric. He clearly hopes to appeal to potential voters from the defunct Referendum Party. He is much more likely to prove to pro-European Conservatives he is incapable of representing them."
Privately, some Tory MPs are worried that the party could be hit by a "pincer movement" of the Pro Euro Tories on the one hand, and the UK Independence Party, which wants to leave the EU, on the other.
Yesterday, the Tories warned that the British National Party might attract votes in the London region because its name would appear at the top of the lengthy ballot paper with an arrow next to it, because the parties were listed in alphabetical order.