Two members of the Government are resigning and a Cabinet minster is mulling whether to quit over Brexit this weekend as Theresa May’s administration appears to be disintegrating ahead of the most important vote of a generation.

Government whips have given Conservative MPs until lunchtime on Sunday to set out how they will vote on Mrs May’s Brexit deal, in a desperate bid to judge the scale of a rebellion that threatens to bring down her government.

Writing in The Telegraph, Will Quince MP, a member of the Defence Secretary’s ministerial team, announces he is quitting his government role, saying he wants to “implore the Prime Minister to go back to the European Union and find another way”.

A second Parliamentary Private Secretary, who The Telegraph has been asked not to name at this stage, has also told whips that they will quit on Monday, while a number of senior party figures were “wrestling with decisions to resign”.

More resignations are possible from the Cabinet, with leading Brexiteer Penny Mordaunt said to be deciding over the next 48 hours whether to back the deal or quit in what one minister described as “the week of unknowns”.

In a clear indication that Britain could be on the verge of a re-alignment of politics along Remain/Leave lines, as many as 100 MPs – including 35 Tory MPs – are prepared to publish a motion calling for a vote on the terms of the UK’s exit immediately after Mrs May’s deal is voted down on Tuesday.