Theresa May's honeymoon period at the top of British politics could be over tomorrow (7 December) as the Conservative premier reportedly faces a rebellion from up to 40 of her own MPs over Brexit.
The Tories are expected to back a motion from Labour which calls for "clarity" from the government over its strategy to split from the EU.
Open Britain spokeswoman and Conservative MP Anna Soubry told The Guardian "at least" 20 of her colleagues were ready to rebel against May, while other reports suggested as many as 40 Tory MPs could defy the prime minister.
"This transcends party politics and tribalism. I have to say I can't see anything in it I don't approve of and could not support," Soubry said.
May and her ministers have kept their negotiating position close to their chests, ruling out a "running commentary" on Brexit.
But the government has faced increased pressure from across the political spectrum to disclose more information as May's March 2017 deadline to trigger Article 50, the official mechanism to split from the EU, looms.
The prime minister could also be forced to table an Article 50 bill in parliament after the High Court ruled that MPs must have a vote on the mechanism.
The government is currently appealing the decision at the Supreme Court, with a final ruling in January 2017.
The Shadow Brexit Secretary Sir Keir Starmer will lead Labour's debate tomorrow in the House of Commons.
"This is a real opportunity to finally get clarity on the government's plan for Brexit," he said.
"Labour accept and respect the referendum and we will not frustrate the process of leaving the EU.
"But Parliament and the public need to know the basic terms the Government is seeking to achieve from Brexit. This issue is too important to be left mired in uncertainty any longer.
"That is why Labour have called this debate on Wednesday. Our motion is simple but would deliver real accountability and grip in the Brexit process. I hope MPs on all sides of the House will join Labour in supporting it."