Eurosceptics have set up a “party within a party” with a highly organised whipping operation among Tory Eurosceptic MPs to try to frustrate Theresa May’s Brexit plans.

The news threatens to blow wide open the frustrations within the Conservative Party about Theresa May’s Chequers plan for trading with the European Union after Brexit.

The news has emerged on the day that Brandon Lewis, the party Chairman, and Gavin Barwell, the Prime Minister’s Chief of Staff, hosted a conference call with senior members of the voluntary party to gauge the mood among the grassroots about the Brexit proposals.

More than 100 Eurosceptic Tory MPs are now on a WhatsApp group co-ordinated by former Brexit minister Steve Baker who is giving them voting instructions.

The combination of grassroots anger and an organised Eurosceptic backbench party run by Mr Baker - who ran the Conservatives for Britain group which helped to force David Cameron to commit to an EU referendum when he was Tory leader - will be Mrs May's worst nightmare.