David Cameron faces a three-pronged attack from eurosceptic Conservative MPs as they threaten to join forces with Labour and the SNP to force a defeat on the Government over its proposed rules for the EU referendum.

Eurosceptics will attempt to force the Government to implement the full “purdah” rules during the referendum campaign, try to force through rules banning EU institutions from spending on the referendum campaign and aim to defeat plans by ministers to allow a snap referendum to be called by the Prime Minister, which could lead to a four-week campaign rather than the usual 10-week battle.

In a further sign of trouble ahead for the Prime Minister, a shock new poll found that British voters were now ready to quit the EU – the first major poll to show the ‘Out’ campaign ahead.

In what could be an embarrassing defeat for the Government, Tory rebels are considering joining Labour and potentially even the SNP in forcing Mr Cameron to honour the normal purdah rules in the run-up to the vote, which could be held next year.

In a bid to appease Tory rebels, Mr Cameron last week backed down on his refusal to impose the full purdah rules, which ban official government resources being used to make a case for either side in a referendum or election. However the changes did not go far enough to win over Eurosceptic rebels.

According to sources within the Tory rebel camp, the Government is facing a major defeat over the rules for the European Union referendum with up to 50 Eurosceptic Conservative MPs planning to rebel (Getty)

A further demand in an amendment tabled by Steve Baker, co-chairman of the anti-EU Conservatives for Britain group, is demanding that all EU institutions are banned from directly funding the ‘Yes’ campaign. The MP for Wycombe fears that a spending splurge by the EU Commission on propaganda will harm their chances of winning a ‘No’ vote, claiming pro-Brussels campaign literature skewed the playing field in referendum campaigns on the 2009 Lisbon Treaty vote in Ireland and Croatia’s referendum on EU membership in 2012.

Steve Baker, co-chairman of the anti-EU Conservatives for Britain group

The Conservatives for Britain group has written to 115 MPs calling on them to back the move to stop the EU “from direct campaigning in the referendum, whether under the guise of EU law or otherwise”.

Mr Cameron is also braced for defeat over an amendment the government has tabled that would allow it to force the Electoral Commission to decide who will run the ‘Yes’ and ‘No’ campaigns long before the date of the referendum is announced, instead of appointing them at the start of a 10-week campaign.

This has led to accusations from eurosceptics that Mr Cameron is trying to change the law so he can call a snap referendum involving a four-week campaign instead, leaving no time to make the argument for a Brexit.

Liam Fox, who served as the Defence Secretary under Mr Cameron’s last government, told the Sunday Times: “To try to change these rules is substantially wrong and politically inept because the legitimacy of the referendum result will depend on the perception of fairness and process.

“If people perceive that the dice were loaded in favour of one side, rather than settling the issue for a generation, it will become a running sore in our politics.”

Eurosceptic Tory MPs Show all 7 1 /7 Eurosceptic Tory MPs Eurosceptic Tory MPs Owen Paterson Formerly a cabinet minister, Owen Paterson is now free to make his opinion known on the backbenchers. On the subject of Europe, he does so regularly – claiming recently that the EU referendum was “rigged” in favour of staying in Getty Eurosceptic Tory MPs John Redwood A longstanding eurosceptic, Mr Redwood warned last year that businesses that spoke out in favour of EU membership would be punished at the check-outs by anti-EU Getty Eurosceptic Tory MPs Bill Cash Awkward squad rebel Bill Cash said last year that he thought the EU had become an undemocratic, German-dominated project. “An increasingly assertive German Europe is at odds with British national interests,” he wrote in the Daily Telegraph Getty Eurosceptic Tory MPs Philip Davies From the Conservative party’s hard right wing, Philip Davies has been a longstanding critic of the EU. He founded the Better off Out campaign and is so eurosceptic that Ukip decided not to stand a candidate against him in 2010 because they agreed with him Rex Eurosceptic Tory MPs Nadine Dorries Outspoken Tory MP Nadine Dorries has previously advocated an alliance with Ukip. At the height of the Greek crisis in 2013 she said that the EU was “dying on its feet” Rex Eurosceptic Tory MPs Liam Fox The former defence secretary is a central figure on the right wing of the Conservative party. He’s long put pressure on David Cameron over EU negotiations Getty Eurosceptic Tory MPs Zac Goldsmith A socially liberal eurosceptic, Goldsmith was one of the founding members of the People’s Pledge campaign to get MPs to sign up for an EU referendum. His father ran the Referendum Party, a precursor to Ukip Getty