At least 15 Tory MPs have announced their intentions to vote with Labour against locking the Brexit date into law.
Tory MP Bernard Jenkin said: “Anyone who voted for Article 50, but then does not wish to fix the date, they are open to the charge that they do not actually want us to leave the European Union.”
Every member of the group except staunch Remainer Kenneth Clarke originally voted to invoke Article 50 which started a two-year countdown to the UK ditching Brussels.
The group is thought to be enough to overturn Mrs May’s majority which stands at around 11 on Brexit issues.
The rebel MPs, who mostly represent Leave-voting constituencies, are expected to come under significant pressure in the build up to the vote.
Remainer Tory MP Anna Soubry last night claimed the “bullying had begun”.
The Tory rebel’s scheme has been given extra weight following the decision to give Parliament a vote on the deal David Davis gets from the EU.
Labour has dismissed the attempt to enshrine the divorce date in law as a “gimmick” from the Prime Minister but eurosceptics fear it is needed to prevent a last minute betrayal following the move to give MPs a vote on the final deal.
Mr Davis defiantly revealed earlier this week that if MPs vote against his deal the UK would just leave the European Union with no deal.
Led by former attorney general Dominic Grieve the MPs include senior Tories Nicky Morgan, Mr Clarke and Ms Soubry.
They will join Jeremy Corbyn’s ranks who have already confirmed their intentions to vote against the bill that they claim is “pandering” to Brexiteers.
Mr Clarke who has publicly stated he wishes to reverse Article 50 and stop Brexit was treated to a standing ovation from the Opposition benches after his speech in which he declared he was a “rebel”.
While Labour jeered their own MP, Frank Field after he declared the party “needs educating” as many of its supporters voted Brexit.
Mr Clarke said: “I’m the rebel. I espouse the policies that the Conservative Party has followed for the 50 years of my membership of it until we had a referendum 18 months ago.
“I regret I have not yet seen the light. There are some very, very, very serious issues to settled in this Bill.”
News of the “mutiny” comes as veteran Remainer Vince Cable was slammed as he continued his calls for a second referendum.
Radio host Julia Hartley-Brewer accused the Liberal Democrat leader of being unwilling to accept the Brexit vote.
Speaking on her TalkRADIO show, she reminded Sir Vince the British public had voted to quit the European Union.
As the party leader said the public were not aware of what a Brexit vote meant, Ms Hartley-Brewer highlighted the 1975 EU referendum saying British voters were not aware then how the Brussels bloc would turn out.
Ms Hartley-Brewer said: “The choice of remaining in the EU was available back in June 2016, I think we had our say on that.”
FULL LIST OF MPS
Heidi Allen MP
Stephen Hammond MP
Nicky Morgan MP
Oliver Heald MP
Jonathan Djanogly MP
Sarah Wollaston MP
Vicky Ford MP
Bob Neill MP
Dominic Grieve MP
Kenneth Clarke MP
Antoinette Sandbach MP
Paul Masterton MP
Tom Tugendhat MP
Jeremy Lefroy MP
Anna Soubry MP