Yvette Cooper, a senior Labour MP, and Sir Oliver Letwin, a senior Conservative MP, have been rallying support for a proposal that would force the government to hand power to parliament if no UK-EU withdrawal deal has been approved by March 13.
Under the proposal, which is set to be tabled as an amendment on Wednesday, the government would be legally obliged to offer MPs the option of requesting an extension in the Article 50 exit process beyond March 29.