TORY Eurosceptics are preparing to ambush Theresa May by unveiling their ‘Clean Brexit’ policy paper next month, the Sun can reveal.

Arch-Brexiteers want to deliver a vision for an “alternative to Chequers” just days before a critical Tory party conference.

Eurosceptics are incensed by the PM’s Chequers proposal - claiming a bid to stay in a single market for goods will tie the UK to EU rules for years to come.

The plans are believed to have the support of Jacob Rees-Mogg, head of the Tory MPs ‘European Research Group’.

Ex-Cabinet Minister Peter Lilley and John Redwood are looking at tariffs and trade options. It will put intense pressure on No.10 in the run-up to a party conference that could decide her fate.

One source told The Sun: “This is about delivering the clean Brexit that people voted for. No concessions.”

The revelation came as Tory party bigwigs sparked backlash by urging local associations to back the PM’s Chequers plan on the doorstep.

Conservative HQ was branded “moronic” by Eurosceptic MPs after asking regional branches to spend a small fortune on leaflets backing the PM’s soft Brexit plan.

Maria Caulfield, who quit as vice-chair of the Tory Party over Chequers, said local officers and councillors were furious. Posting on a Tory Whatsapp group she stormed: “Are the power that be determined to add insult to injury after the white paper, Boris, the PM letter and now this.”

Marcus Fysh, a Eurosceptic who has called for the PM to go, added: “Uttterly moronic I’m afraid. The sooner this administration is changed the better.”

They also hit out over the “Lib Dem Yellow” colour of the mailout – which explains how the Chequers proposal will end free movement, and the rule of the European Court of Justice.

Brexit backers argue the PM’s plan to keep Britain in a single market for goods will force the UK to be subject to ECJ rulings for years. Separately yesterday, sources in Brussels conceded the EU could suffer more than the UK in the immediate aftermath of a No Deal Brexit.

They claimed officials drawing together desperate contingency plans to keep trade links open and aircraft flying are worried whether EU institutions and EU member states will be able to act swiftly enough.