British Prime Minister Theresa May could see up to 40 lawmakers from her conservative party also demanding she publish her plan for Brexit before starting negotiations.
The rebellion might be enough to push the opposition motion through the 650-seat House of Commons on Wednesday.
And that would be a symbolic blow against May’s refusal to provide a “running commentary” on her strategy for withdrawing from the European Union.
The government is fighting a legal challenge at the Supreme Court. The battle is aimed at stopping parliament from having the final say on a decision to trigger Article 50 of the EU’s Lisbon Treaty, which would begin formal exit negotiations.
Brexit supporters fear that MPs, overwhelmingly in favour of staying in the EU, might seek to delay the process or soften the terms of the break.
The motion by the opposition Labour party “calls on the prime minister to commit to publishing the government’s plan for leaving the EU. The party has asked her to do that before Article 50 is invoked.”That is a process May says will happen by the end of March.
In a nod to the government’s concerns, it also “confirms there should be no disclosure of material that could be reasonably judged to damage the UK in any negotiations.”
Former Conservative minister Anna Soubry, a rebel in her party because of her opposition to Brexit, said she would support the Labour motion and “20, 40” of her colleagues may follow.
She said the proposal was “eminently sensible and supportable”.
“The best solution would be for the government to unite all sides of the House by now agreeing to put before parliament their plan for the upcoming negotiations,” she said.
May will be in Bahrain on Wednesday for a meeting of the Gulf Cooperation Council, while a number of her ministers are also out of the country. It then reduces the government’s already slim majority of 13 in the House of Commons.