Jacob Rees-Mogg has warned the Prime Minister people did not vote for a Corbyn-May coalition.
European Research Group (ERG) chairman Mr Rees-Mogg criticised the Prime Minister for planning to collaborate with “a known Marxist” in Labour leader Jeremy Corbyn.
The Conservative MP for North East Somerset said the move would lose Tory votes, and warned history did not show success for political leaders who tried to get policy through the Commons “on the back of Opposition votes”.
Speaking after a meeting about Theresa May’s latest statement, Mr Rees-Mogg said: “I think getting the support of a known Marxist is not likely to instil confidence in Conservatives.
“This approach to Government is an unsuccessful one and it also lacks democratic legitimacy.
“People did not vote for a Corbyn-May coalition Government – they voted for a Conservative Government, which became a confidence and supply with the DUP.
“This is a deeply unsatisfactory approach – it’s not in the interests of the country, it fails to deliver on the referendum result and history doesn’t bode well for it.”
Mr Rees-Mogg cited the examples of former prime ministers Robert Peel, who was forced to resign and split the Tory party, and Ramsay MacDonald. who was forced to resign after including opposition leaders in a cross-party national government.
However, he claimed to still support Mrs May as leader and, although he “didn’t whoop and holler with delight”, neither did he expect “a glorious outcome” from the Prime Minister’s statement.
The Conservative MP for North East Somerset said he had been willing to accept a “second-rate” Brexit rather than to hold out for something “perfect” and end up with no Brexit.
When asked if he could back a deal struck with Jeremy Corbyn, he told journalists “Well, I wouldn’t hold your breath – I’m not a Marxist in case you hadn’t noticed.”
He added: “What was announced today was an attempt to overturn the referendum that wanted a clear Brexit, to do a deal with a socialist who doesn’t want Brexit and is not in line with the Conservative Party’s manifesto commitments or with the referendum.
“This is all about getting further and further away from the Brexit people voted for, which is very serious.”
ERG member Andrew Rosindell said he was “shocked and dismayed” as he left the meeting.
Another ERG member, Simon Clarke, retweeted former foreign secretary Boris Johnson and commented “This is absolutely right from Boris Johnson. Tonight’s statement is incredible”.
Mr Johnson had tweeted: “It is very disappointing that the cabinet has decided to entrust the final handling of Brexit to Jeremy Corbyn and the Labour Party.
“It now seems all too likely that British trade policy and key law making powers will be handed over to Brussels – with no say for the UK.
“As it is, we now face the ridiculous possibility of being forced to contest the European elections more than three years after leaving the EU and having to agree to exit terms that in no way resemble what the people were promised when they voted to leave.”
The MP for Uxbridge and South Ruislip added “under no circumstances” would he vote for a deal involving a customs union.
He tweeted: “The PM and cabinet have concluded that any deal is better than no deal, and this is truly a very bad deal indeed – one that leaves us being run by the EU.
“I can under no circumstances vote for a deal involving a customs union as I believe that does not deliver on the referendum.”