Theresa May is facing fresh unrest from Eurosceptic Tory MPs who are plotting a major campaign to push her into delivering a “hard Brexit”.


A new group, Leave Means Leave, launches today with the aim of getting the UK out of the EU’s single market, ending the influence of Brussels on British laws, and scrapping European “free movement” migration.


The group has won the backing of leading Tories, including Dominic Raab, the former justice minister, Owen Paterson, the former environment secretary, and Sir Gerald Howarth, the former defence minister who chairs the Thatcherite Tory group, Conservative Way Forward.


It is led by the businessman Richard Tice, one of the leading figures behind the Leave.EU campaign in the referendum, with the backing of other business figures, MPs and economists.


In the group’s launch report, it argues that Britain must pull out of the EU’s single market, even if no alterative trade deal has been struck with Brussels.


Mr Tice said: “Let’s be clear: No deal is better than a bad deal.”


The campaign comes at a critical time for Mrs May and her ministers, who are wrestling with the complex process of drawing up the government’s priorities for what Britain’s future relationship with the EU should be.


The Prime Minister has so far declined to give any details of what she will seek to achieve in exit talks with the EU, or exactly when she will begin the formal negotiations.


In private, Tory MPs are growing impatient for her to spell out details and want her to put “flesh on the bones” of her “Brexit means Brexit” pledge at the Conservative party conference next month.


The new group, which has the support of at least six Conservative MPs so far, will add to the impression that concerns are growing among Mrs May’s colleagues over whether she will deliver full Brexit or some kind of compromise.


Last week, John Whittingdale, the former cabinet minister, demanded that Mrs May trigger the formal “Article 50” process for withdrawing from the EU within “weeks” in order to kill off attempts to keep Britain in the EU.


The new group backed Mr Whittingdale in calling for Brexit sooner rather than later.


Mr Tice told The Sunday Telegraph: “The British people made it clear that they wanted to leave the EU. There should be no compromise on this. The sooner we leave the more certainty and confidence for everyone.”


The Prime Minister has said she will wait until next year before triggering Article 50 of the European treaties, which would launch the formal two year process for negotiating the terms of Brexit.


Mr Tice suggested she should aim to complete the talks sooner. This would set Britain free to sign trade deals with countries outside Europe and would be a signal to the EU that the UK is serious.


“Also consumers and businesses can draw confidence that we are a globally focussed strong economy,” he said.


The group argues that remaining in the single market would be a mistake after leaving the EU because this would mean the UK would still be bound to accept unlimited numbers of migrants, while British companies would all have to abide by Brussels law.