David Cameron is facing a "mutiny" over the vote on holding a referendum about Britain's future in Europe with a number of ministerial aides poised to quit, it was claimed today.
At least 60 Conservative MPs have backed a motion calling for a national poll and senior party figures today pledged to defy the leadership if it ordered them to oppose the plans.
Labour has seized on Tory "squabbling" as proof the Government is "split from top to bottom" on the issue.
Shadow Commons leader Angela Eagle told MPs there were "reports of at least five ministerial aides on the brink of resignation" over the in/out referendum vote and accused the Prime Minister of "running scared".
Conservative Stewart Jackson revealed he was one of those who would quit his junior position in Government.
The parliamentary private secretary to Northern Ireland Secretary Owen Paterson told the BBC that Europe was a "totemic issue" for the party.
"My constituents are saying 'your three-line whip is from us and we think the people's voice should be heard'," he said.
"I will vote in favour of the motion and, in so doing, I will very likely relinquish my position as parliamentary private secretary to the Secretary of State for Northern Ireland, which will disappoint me but some things are more important than party preferment."
Mark Pritchard, secretary of the influential backbench 1922 Committee of Tory MPs, told the Commons today there was "now a three-line whip from the Government on the Conservative benches".
He added: "Is it any surprise that the British public are increasingly frustrated that this place is more out of touch than ever on the European question?"
Mr Pritchard earlier claimed it was a matter of "country first, party second" when confirming he would defy the party line.
Downing Street has said Mr Cameron expected Conservative MPs to vote against the proposals and a spokesman tonight refused to comment on its whipping arrangements.
The Government has until tomorrow afternoon to table a wrecking ammendment to the motion, which calls for the country to be given a three-way choice between remaining in the EU, leaving or negotiating the terms of a looser relationship "based on trade and co-operation".
Mr Cameron and Foreign Secretary William Hague were set to miss the showdown with eurosceptics, originally planned for Thursday, because of a Commonwealth summit in Australia.
The debate has been brought forward to Monday to allow Mr Hague to spearhead the Government response and the Premier to attend, although it is not yet clear whether he will cast a vote.
Eurosceptic Conservative MP Bill Cash said: "The prospect of an intervention by the coalition Government is beyond belief.
"Why should the Government prevent the British people from having their say, especially when the European project is quite clearly failing?"
The debate will follow a statement by Mr Cameron on the weekend's European Council meeting in which he is expected to set out his position.
Asked whether the Prime Minister was concerned that the impending Commons vote would cast a shadow over this weekend's crucial meetings of EU leaders and finance ministers in Brussels, a spokesman said: "What we are focused on, and our priority, is that we see a resolution to the problems in the eurozone."
Labour and the Liberal Democrats are subjecting their MPs to a three-line whip.
Labour leader Ed Miliband said: "The prospect of a referendum would create economic uncertainty our country does not need right now.
"David Cameron should show some leadership. He should not be spending the next few days negotiating with his backbenchers but negotiating for Britain to sort out the eurozone crisis.
"They are looking inwards. They are out of touch. They are squabbling about Europe and not fighting for Britain."
An amendment to the motion apparently designed to head off a Tory rebellion was tonight tabled by backbench MP George Eustice.
Mr Eustice, who as a former press secretary to Mr Cameron is seen as close to Downing Street, emailed fellow Tory MPs with the amendment and urged them to back it.
It calls for the Government to start renegotiating Britain's relationship with the EU before holding a referendum on the results of that process.
In his email, Mr Eustice suggested the amended motion "more closely reflects the views of the majority of the parliamentary party".
"The advantage of having a referendum after the renegotiation rather than before is that the public would then be able to judge whether or not the Government had succeeded and this would put pressure on the Government to negotiate forcefully," he said.
He stressed it was "not yet" backed by the Government, but added that it was committed to taking on board representations
"I would therefore urge any backbench MPs who feel closer to this motion than the one currently tabled to add their names to it," he said.
"Likewise, I would urge any frontbench MP who would like the opportunity to vote in favour of the motion rather than be ordered to follow Ed Miliband through the voting lobbies to make their views known to the Prime Minister's office."