Prime Minister Boris Johnson could face a rebellion from Brexiteer Tory MPs if he only seeks to renegotiate the backstop of the EU-approved withdrawal treaty, with Leavers warning the deal “binds the UK into a permanent relationship with the EU”.

Mr Johnson’s office has said that while the prime minister is ramping up no-deal preparations, he will be using momentum following from the G7 summit last weekend to push for the reopening of Brexit negotiations with the EU and has sent his Brexit negotiator David Frost to talk with bureaucrats in Brussels.

Mr Frost’s spokeswoman told The Mirror that the prime minister would be willing to accept the rest of the withdrawal treaty if the Irish backstop — which could lock the EU in regulatory alignment with the bloc post-Brexit — is removed, saying: “We have been clear that the changes we are seeking relate to the backstop.”

This raised alarm bells with Brexiteer Tories, dubbed “The Spartans”, who say that removing the backstop is not enough, warning that the treaty is not just a temporary arrangement, but is the blueprint for a future relationship and would result in a soft Brexit where the UK remains closely aligned to the EU in terms of regulation, permanently obstructing free trade with the rest of the world.

The Spartans had also expressed concern over the near two-year transition period, during which the UK cannot initiate its own bilateral trade deals with third countries, with Mr Johnson having said that if he is successful in renegotiating the backstop and the treaty is signed off, the transition period could mean the UK staying in the Customs Union until 2021. Concerns also remain over defence and security issues, and the continuing supremacy of EU law under the terms of the withdrawal treaty, and there is opposition to paying the £39 billion divorce bill.

When HuffPost UK asked Steve Baker MP — who turned down a “powerless” position in Johnson’s cabinet while the prime minister elevated some Remain voters to higher positions — for comment, the senior member of the European Research Group said: “The withdrawal agreement is not merely about the mechanism for our withdrawal and arrangements in the short term. It in effect binds the UK into a permanent relationship with the EU in which it remains subject to many of the constraints of membership while having no vote.”

An ally of Prime Minister Johnson told HuffPost UK: “We know that the ‘Spartans’ are going to accuse us of betrayal at some point.” A previously-reported 40 to 60 Conservative MPs could block a Johnson EU bill, forcing the defeat of the government bill.

Many of the Spartans reportedly only backed Boris Johnson during the leadership race because he had pledged that he would not be pursuing the treaty, agreed by his predecessor Theresa May. Mr Johnson shocked Brexiteers when after voting against the Withdrawal Agreement Bill twice, he backed it on the third vote. Brexit Party MEPs warned last month that “we can’t believe Boris” on his pledges to deliver Brexit, and that attempts to submit a rehash of May’s deal will result in the Tories suffering politically.

Brexit Party leader Nigel Farage warned Johnson on Tuesday that his party will “fight you in every single seat up and down the length and breadth of the United Kingdom” if he tries to force a watered-down May treaty, saying: “The Withdrawal Agreement is not Brexit, it is a betrayal of what 17.4 million people voted for.”

Prime Minister Johnson announced on Wednesday that he would be proroguing (suspending) parliament ahead of a new Queen’s speech on October 14th, beginning a new session of parliament. While outraging Remainers — who have been plotting to overthrow the Johnson government and stop Brexit — in the belief it is a means of forcing a no-deal Brexit, the government still holds out that an amended deal could be passed before October 31st.

Mr Johnson is hoping that if an amended treaty is agreed at the European Council summit on October 17th-18, he will put forward a Withdrawal Agreement Bill to be voted on in the last week of October. If not passed, there should then be a no-deal exit.