Theresa May has been accused of being "too weak" to face down hard Brexiteers in her party after more than 60 Tories set out their demands for the next stage of exit talks.
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.
In a letter, Conservative 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 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.
The Government should publish a mandate showing how the UK wants to approach trade with the rest of the world.
"The UK must be free to start its own trade negotiations immediately," the letter adds.
"The UK should negotiate as an equal partner. Ministers may not want or be able to accept the EU's timing and mandates as fixed, and should be able to set out alternative terms including, for example, building an agreement based on our World Trade Organisation membership instead.
"Any 'implementation period' should be based on WTO principles. Any implementation period must not restrain the UK from negotiating or signing other trade agreements."
Mrs May is meeting Dutch Prime Minister Mark Rutte for talks in Downing Street and is expected to update him on Brexit progress.
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.
"Not satisfied with hijacking the referendum result for their own extreme ends, now May's militants, now called Maymentum, are hijacking the Conservative Party - one nation, pro business, common sense Tories must fight back for the good of our country.
"And 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.
"It is clear from this list of demands that the Tories don't want either a transition deal or a ?future relationship with the EU. It is time for the Prime Minister to put country before party and say no to her hard right Brexiteers."