The leader of Tory MEPs, Lord Plumb, will today launch a counter-attack on the Euro-sceptics as "dishonest and disreputable" in a speech in Luxembourg.
He is expected to accuse the "disaffected" Tory MPs of using the single European currency to challenge Mr Major's leadership. Warning it could lead to defeat at the next election, Lord Plumb will say: "It is disloyalty of the highest degree."
The MEPs have called a Tory conference in Nottingham on 8 July to put their case. The Positive European group of Tory MPs, led by Ray Whitney, a former minister, has called for a meeting with the Prime Minister before then, to warn him not to bow to further pressure from the Euro-sceptics.
Some senior ministers believe the Prime Minister's meeting with the Euro-sceptics was a mistake, leaving him looking weak and raising the prospect of a leadership challenge in November.
"He was very depressed by it," one ministerial source said. "He should never have agreed to meet them. It's pretty clear what they are up to. They are just pushing him inch by inch to accept their line."
Mr Major's allies are angry that the Euro-sceptics used the meeting to ambush the Prime Minister, and to present their views as the majority opinion on the Tory back benches. But there is also growing dissatisfaction among Europhiles with Mr Major's readiness to deal with the Europhobes.
Their exasperation increased as details of the confrontation emerged at Westminster. The Prime Minister was frequently interrupted, and heckled by the MPs who showed little respect for his authority.
At one point, Iain Duncan-Smith, the Tory MP for Chingford, bluntly told the Prime Minister: "You haven't answered the question." Mr Major insisted he could not be boxed in by giving away his negotiating position before talks with European leaders.
Sir Ivan Lawrence, a senior Tory backbench lawyer, was cheered by other backbenchers when he told Mr Major that the Conservatives would not win the next election on their existing policy.
The anger of the Euro- sceptics raised the likelihood of a challenge to his leadership, in spite of the threat that it could lead to his replacement by Michael Heseltine.
There was speculation on the right wing that Mr Heseltine would seek to win over their votes by making Michael Portillo his deputy in a twin ticket for the leadership.
Some on the centre of the party last night indicated that they were prepared to abstain to put pressure on Mr Major to resign.
"If nothing changes between now and November, there will be a hundred of us who will abstain. That is enough to kill him," one Major supporter said.Reuse content