The move by Kenneth Clarke, Michael Heseltine and Sir Edward Heath infuriated Eurosceptics and deepened the Tory divide on Europe on the eve of the party's annual conference in Bournemouth.
It also raised the prospect of a permanent split in the Conservative Party after the pro-Europeans campaign alongside Mr Blair, who is likely to call a referendum on the euro shortly after the next general election.
Although backbench Tories would be allowed to call for a Yes vote, the referendum could mark the parting of the ways. The crucial factor could be Mr Blair's decision on whether to introduce proportional representation (PR) for House of Commons elections, a move that could persuade pro-European Tories to run under their own colours.
"We are not planning a breakaway, but the fact is that PR would reshape British politics," one leading Europhile said last night.
Today Mr Hague will claim his critics are isolated when the party announces the result of the ballot of its 340,000 members. By a margin of about four to one, they are expected to endorse his policy of staying outside the single currency in this Parliament and the next.
Yesterday the Tory leader suggested that those who refuse to accept the official position should consider their place in the party. "I will be saying to that remaining minority `well, take it or leave it'," he said.
In a boost for Mr Hague, the turnout looks certain to exceed 50 per cent, making it harder for his critics to deny he has a mandate for his hard line.
But the Europhiles will argue that less than half the membership has endorsed his policy and were adamant yesterday that, whatever the result, they would not be silenced. "The argument is certainly not over," said Mr Heseltine, the former deputy prime minister. He had "not the slightest doubt" there would be "trans-party alliances" if Labour made up its mind to join the euro.
Sir Edward, the former prime minister, said he would share a platform with Mr Blair during the referendum campaign, but insisted that would not mean he was abandoning the Tories.
In an interview with The Independent, Sir Edward dismissed Mr Hague's referendum on the euro as "meaningless" and said that it "won't impress anybody".
Mr Hague hit back yesterday by attacking the party's pro- Europe old guard as people who "have had their day".
He told ITV's Jonathan Dimbleby programme: "I have to go on without them, I have to take the party on and say those people are in the past now, they are irrelevant to the future of the party."Reuse content