Nearly 20 Tory MPs are threatening to rebel against the Government's plans to enshrine the date of Brexit in law including seven former ministers and two committee chairs.
The MPs confronted Julian Smith, the new chief whip, during a meeting on Monday to express their fury at the Government's plans.
The rebels include many Tory MPs who are usually loyal to the Government but are concerned that fixing the date of Brexit to March 29, 2019 will "tie our hands" in negotiations.
Those present at the meeting said that it had been "brutal" for Mr Smith as MPs vented their fury about the Government's plans.
The Telegraph understands that 18 Tory MPs attended the meeting - more than enough to defeat the Government if Labour joins them in voting against the Government's amendment next month.
Tom Tugendhat, the chairman of the Foreign Affairs select committee, was among those who attended.