Theresa May has been accused of being "too weak" to face down hard Brexiteers in the Conservative Party after more than 60 MPs set out their demands for the next stage of EU exit talks.
In a letter, Tory Eurosceptic MPs warned the UK must have full control over laws after Brexit and must not become a "rule taker".
Britain must not be stopped from negotiating and signing trade deals during any transition period, they said.
The prime minister will hold a crunch meeting with senior Cabinet ministers on Thursday to thrash out an agreement on how to proceed in negotiations with the European Union.
The letter was sent by the European Research Group (ERG), made up of Tory Eurosceptics, and was signed by 62 MPs, including former Cabinet ministers Priti Patel and Iain Duncan Smith.
It includes a number of "suggestions" for securing a successful Brexit, including "taking control" of World Trade Organisation tariff schedules that regulate trading.
Labour said the letter exposed the "deep divisions" in the Conservative Party.
Paul Blomfield, shadow Brexit minister, said: "It is clearer than ever that Theresa May cannot deliver the Brexit deal Britain needs.
"She is too weak to face down the fanatics in her own party and to deliver a final deal that protects jobs and the economy."
Former Liberal Democrat leader Tim Farron, a supporter of the Best For Britain against Brexit, said: "It seems the Prime Minister has one arm tied behind her back by the Tory militants who are now nakedly acting like a party within a party."
"The PM must listen to the people, not to the far-right faction who are launching this shameless coup."
SNP foreign affairs spokesman Stephen Gethins said: "The process for leaving the EU has been hijacked by hard right Tories whose agenda for Brexit at any costs will be devastating for us all in terms of jobs, the economy and opportunities for young people in the future."