Conservatives in disarray as 70 MPs threaten revolt over EU

David Cameron is today facing the prospect of the largest Commons rebellion of his premiership, with dozens of Conservative MPs likely to defy the Government and vote for a referendum on Britain's EU membership.

With little sign yesterday that the rebellion was fading or that Downing Street was prepared to make concessions, rebels predicted that more than 70 MPs would ignore a three-line whip and vote against the Government. While the amendment will certainly fail because of Labour's support for the Government, a significant rebellion would be embarrassing for Mr Cameron, especially if it is backed by more than 75 MPs – the Coalition's notional parliamentary majority.

Political analysts believe the result could be the largest rebellion in history by Conservative MPs when in government over the issue of Europe, as well as the biggest vote against the Government by Conservative MPs since the election.

In a sign of the growing acrimony on the Tory benches, one senior party member accused William Hague, the Foreign Secretary, of "insulting MPs' intelligence" by claiming that such a vote would be damaging in a time of economic uncertainty.

There were further claims that government whips were using "bully-boy" tactics to try to see off the rebellion. Some MPs have allegedly been told they could be blacklisted from being a minister for four years if they defy the Government, while others have been warned that Conservative HQ will not support them in attempts to get reselected after planned electoral-boundary changes.

Mr Cameron suggested in Brussels yesterday that the "possibility" of an EU treaty change referred to in yesterday's summit conclusions could give Britain a chance to reclaim powers. "Any treaty change – as the last treaty change did – is an opportunity for Britain to advance our national interest," he said.

But there was little sign yesterday that the rebels could be bought off or that Mr Cameron would back down and give MPs a free vote on the amendment, which in any case would not be binding on the Government. "My sense is that, having made their decision, they're planning to try and shoot their way through," one MP said. "But I have no reason to think that the 68 MPs who put their name to the amendment are going to back down now – and many more will abstain. This is a fiasco of the Government's own making."

Rebel MPs pointed out that it was the Government's decision to launch the e-petition website – promising the prospect of parliamentary votes on petitions which gathered more than 100,000 signatures – which led to the situation arising in the first place. They added that the rebellion was popular among grass-roots Tories.

"The origins of this motion came from Downing Street's own e-petitions and thousands of people signed that," said Mark Pritchard, secretary of the Tory backbench 1922 Committee. "Thishasn't been concocted by small groups of Conservative MPs. It has been brought about by the public from a clear, open and transparent process. The Government should step aside from the three-line whip and just allow members to represent the views of their constituents – that is all I am trying to do."

George Eustice, the MP whose compromise amendment on the issue was rejected by the Government, said: "The reason the Government has got a bit of a problem with its backbenchers is there is a feeling, rightly or wrongly, that the Government wants to put this in the deep freeze and forget about the issue. But at a time when we have got a recession looming again, we have got to think outside the box and really be radical."

Richard Ottaway, chairman of the Commons Select Committee on Foreign Affairs, said he would vote with the Government: "It is the right motion at the wrong time," he told The Independent.