Hardline pro-Brexit Tories are struggling to gather support for a leadership challenge against Theresa May, despite days of threats.

The European Research Group (ERG) boasted that it would secure the 48 signatures it needs on Monday, but faced the embarrassment of a backlash that offered the beleaguered prime minister some relief.

Some Tories appeared to have pulled back from submitting letters of no confidence after discovering Conservative members in their constituencies remained loyal to Ms May.

Steve Baker, the ERG’s deputy chairman, faced accusations that he had “overplayed his hand” and overestimated support for a challenge, just days before the crucial EU summit to seal the Brexit deal.

Nick Boles, a pro-EU backbencher, launched an attack on Jacob Rees-Mogg, the head of the ERG, and on Boris Johnson – who is rumoured to have submitted his own letter.

“Do my colleagues not understand how normal people react when they see a group of middle aged men, led by two plummy-toned Old Etonians, trying to bully a conscientious and determined woman out of her job?” he tweeted.

Mr Baker had predicted that “the line will be crossed by a big margin on Monday evening” – but admitted that was “if everyone does what they’ve told me”.

Just 26 Conservatives have announced they have put in letters to Graham Brady, the chairman of the backbench 1922 Committee, although others have made it known privately.

Cabinet ministers resign over Brexit deal Show all 13 1 /13 Cabinet ministers resign over Brexit deal Cabinet ministers resign over Brexit deal Esther McVey Britain's Work and Pensions Secretary Esther McVey arrives to attend the weekly meeting of the cabinet at 10 Downing Street in London. - Britain's Work and Pensions Secretary Esther McVey resigned from the cabinet over draft Brexit deal AFP/Getty Cabinet ministers resign over Brexit deal Handout image taken from the Twitter feed of @EstherMcVey1 of the resignation letter addressed to Prime Minister Theresa May from Works and Pensions Secretary Esther McVey. PRESS ASSOCIATION Photo. Issue date: Thursday November 15, 2018. Ms McVey has resigned, saying the Brexit deal âdoes not honour the result of the referendumâ. See PA story POLITICS Brexit. Photo credit should read: @DominicRaab/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. PA Cabinet ministers resign over Brexit deal Dominic Raab British Brexit Secretary Dominic Raab give a press conference at the end of the final round of talks in Brexit negotiations at the European Commission in Brussels, Belgium EPA Cabinet ministers resign over Brexit deal Handout image taken from the Twitter feed of @DominicRaab of the resignation letter addressed to Prime Minister Theresa May from Brexit Secretary Dominic Raab. PRESS ASSOCIATION Photo. Issue date: Thursday November 15, 2018. Mr Raab has resigned, saying he âcannot in good conscience support the terms proposed for our deal with the EUâ. See PA story POLITICS Brexit. Photo credit should read: @DominicRaab/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. PA Cabinet ministers resign over Brexit deal Rehman Chrishti Vice Chairman of the Conservative Party Rehman Chrishti tendered his resignation letter this afternoon PA Cabinet ministers resign over Brexit deal Cabinet ministers resign over Brexit deal Anne-Marie Trevelyan Parliamentary private secretary in the Department of Education Anne-Marie Trevelyan resigned stating that she cannot support the deal Cabinet ministers resign over Brexit deal Handout image taken from the Twitter feed of @annietrev of the resignation letter addressed to Prime Minister Theresa May from Anne-Marie Trevelyan, a parliamentary private secretary in the Department for Education. PRESS ASSOCIATION Photo. Issue date: Thursday November 15, 2018. Ms Trevelyan has resigned saying she cannot support the Brexit deal after negotiations âbuilt on the UK trying to appease the EUâ. See PA story POLITICS Brexit. Photo credit should read: @annietrev/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. PA Cabinet ministers resign over Brexit deal Sam Gyimah Universities minister Sam Gyimah resigned on November 30, claiming the government's decision to pull out of the EU's Galileo satellite navigation system as a deciding factor PA Cabinet ministers resign over Brexit deal Shailesh Vara Shailesh Vara who has quit as Minister of State for Northern Ireland, saying he cannot support Theresa May's Brexit agreement, which he said "leaves the UK in a halfway house with no time limit on when we will finally be a sovereign nation" PA Cabinet ministers resign over Brexit deal Cabinet ministers resign over Brexit deal Suella Braverman Brexit minister Suella Braverman has resigned, stating “It is not what the British people, or my constituents, voted for in 2016.” Cabinet ministers resign over Brexit deal Ranil Jayawardena Parliamentary private secretary to the ministry of justice Ranil Jayawardena resigned as he could not back the deal "in good conscience"

The vote of no confidence failed to materialise as:

* Ms May seized on business support for her Brexit plan, saying, in her speech to the CBI conference: “Don’t just listen to the politicians, listen to what business is saying.”

* The prime minister said it was “important” that the transition period ends before the next general election, but gave no guarantee – after the EU suggested it could run until the end of 2022.

* Spain threatened to sink the Brexit deal in a row over Gibraltar, demanding one-to-one “separate discussions” on its future, outside of the main negotiations.

* David Mundell, the Scottish secretary, again threatened to quit if the UK remained tied to EU fishing policies and quotas after 2020.

Downing Street also acknowledged that huge progress still needed to be made if the agreement is to be rubber-stamped by EU leaders in Brussels on Sunday.

The prime minister is expected to head to the Belgian capital sometime this week, to head up the negotiations personally – but they could run on until Sunday itself.

As well as agreeing a date for an extended transition – if needed to avoid the return of a hard border in Ireland – the outline of the long-term relationship must be fleshed out.

That document, separate to the withdrawal agreement, is currently just six-and-a-half pages long, saying virtually nothing about future trade, security or data exchange.

It does commit the two sides to filling in the gaps by “building on the single customs territory provided for in the withdrawal agreement” – to the alarm of Brexiteers, who suspect a permanent customs union.

The prime minister’s spokesman said: “We are adding more detail to the outline political declaration for it to become the future framework.