The government could be forced to publish documents outlining its Operation Yellowhammer no-deal Brexit planning, along with details of private discussions on the reasons behind the decision to suspend parliament.
MPs voted 311 to 302 in favour of a so-called "humble address" compelling the government to publish all of the Yellowhammer documents seen by the cabinet or a cabinet committee since 23 July, when Boris Johnson was appointed prime minister.
Ministers have until 11pm tomorrow to publish the Yellowhammer documents, parts of which have been leaked to the press but which the government has yet to make public. A dossier seen by the Sunday Times last month warned that Britain could face shortages of food, fuel and medicine in circumstances described by Cabinet Office minister Michael Gove as a “reasonable worst-case scenario”.
Gove, who is overseeing the government’s preparations for a no-deal Brexit, told MPs last week that departments had made further progress on its contingency planning since the leak.
Senior advisers to the prime minister must also reveal the discussions they had via text messages, WhatsApp, Facebook, email, Telegram and Signal about the decision to prorogue parliament.
They include Dominic Cummings, Boris Johnson's most senior aide, and Nikki da Costa, the PM's top adviser on parliamentary procedure.
Downing Street has repeatedly denied opposition claims that the controversial move, which means parliament is suspended until 14 October, was aimed at limiting the amount of time MPs had to debate Brexit ahead of the 31 October deadline.
Instead, they have claimed prorogation is normal practice before the start of a new parliamentary session.
But kicking off the Commons debate on the issue, former Tory attorney general Dominic Grieve said he believed the secret messages would show that was false if they were released.
He claimed that he had received information which suggested the prime minister had misled the Queen over the true reasons for the prerogation.
Grieve also claimed that under Johnson, No.10 was riding roughshod over civil service conventions.
"My concern is there is increasing and compelling evidence this trust is breaking down and there is cause to be concerned whether conventions are being maintained," he said.
Responding for the government, Gove described Grieve's move as a "fishing expedition" and insisted civil servants' advice should remain private.
"This convention that advice should be private has applied to governments of all parties throughout the history of the civil service," he said.
Among those who voted either against the government or abstained were the 21 Conservative MPs sacked by the PM last week for backing moves to block a no-deal Brexit.