Meanwhile Labour’s Brexit spokesman Keir Starmer has accused the Prime Minister of “rank hypocrisy”, while former Tory-turned-independent Nick Boles has branded him Britain’s Trump”.
The increasingly febrile atmosphere swirling around Parliament has seen plotters draw up plans to table legislation which would require the Government to seek a further extension to Article 50, which if successful would derail plans to quit the EU on October 31, despite Mr Johnson’s “do or die” pledge.
Mr Letwin tweeted: “This is not a proper way to proceed.
“I expect that Parliament will respond in the only way it can: by legislating next week, before it is prorogued, to prevent a disorderly, undemocratic no deal exit on 31 October.
“I shall certainly be supporting that effort.”
Mr Grieve told the Spectator last week: “I will certainly bring down a Conservative Government if the Prime Minister persists in following a course of action that is so unconstitutional.”
Meanwhile Mr Boles posted: “Johnson truly is Britain’s Trump.
“There is no institution, no relationship and no international commitment that he is not willing to sacrifice to achieve a No Deal Brexit.
“He is turning the Conservative and Unionist Party into the English National Party. He must be stopped.”
Speaking on Radio 4’s Today programme earlier, Mr Boles said: “The hard right has taken over the Conservative Party.
“The Conservative Party has fallen prey to an almost religious obsession with the hardest form of Brexit.”
Brexit was “not necessarily” a hard-right move but “foisting” a no-deal departure on the UK would be, Mr Boles claimed.
Mr Starmer tweeted: “Faced with a disingenuous PM shutting down Parliament, a PM being dishonest about the reason for doing so, a PM not committing to obey the law & the rank hypocrisy of a PM who himself broke the whip, Tory MPs are quite right to take a stand against him.”
Other MPs have also indicated they are ready to dig their heels in, with former Tory MP, now a member of Change UK, Anna Soubry tweeting: “There is a growing sense of outrage, a sense this is no longer our country this is not the British way.
“Suspending Parliament to stifle debate, bullying & blackmailing long serving loyal MPs & threatening to defy the rule of law.
“That’s the way of the far left not @Conservatives.”
Tory MPs who defy the Government are widely believed to be facing expulsion and deselecting, with former Chancellor Philip Hammond describing the plan as “staggeringly hypocritical”.
Also speaking on the Today programme, Justice Secretary David Gauke said Mr Johnson was seeking to “re-align” and “transform” the Tories “in the direction of The Brexit Party”.
He added: “I don’t think there seems to be a huge effort to persuade people to support the government this week.
“They seem quite prepared for a rebellion and then to purge those who support the rebellion from the party.”