Opposition leaders will hold talks on Monday following Boris Johnson’s unveiling of his proposed Brexit deal.
Jeremy Corbyn is due to host SNP Westminster leader Ian Blackford and Lib Dem leader Jo Swinson.
Plaid Cymru’s Liz Saville Roberts, Green MP Caroline Lucas and Change UK’s Anna Soubry will also join the meeting.
Ahead of the summit, Corbyn said the cross-party group will discuss what “next steps” to take to avoid a no-deal Brexit.
Labour has insisted that Corbyn must become prime minister of any caretaker government.
But Swinson has said she would not support moves to install Corbyn in No.10 having argued he would not be able to secure a majority in the Commons.
Johnson has repeatedly insisted he will take the UK out of the EU on the current deadline of October 31.
But under the Benn Act passed by the Commons, he will have to ask the EU to delay Brexit if no deal is agreed by October 19.
Westminster has been consumed be speculation as to how Johnson could bypass legislation and avoid requesting an extension to Article 50 at the same time as obeying the law.
Housing Secretary Robert Jenrick told Sky News on Sunday morning the government had “no plan” what to do if parliament blocked a no-deal exit.
Stephen Barclay, the Brexit secretary, confirmed to the BBC that the government was “talking” to Labour and other opposition MPs to try and persuade them to back the PM’s deal.
He said the government was “considering” holding the vote before the EU summit on October 17.
Wigan MP Lisa Nandy said on Sunday there were 40 Labour MPs who wanted to vote for a deal to avoid a no-deal exit.
But she shot down the idea MPs on her side of the Commons would defy Corbyn to vote with the government.
She said Johnson’s plan would not work because it had “virtually no chance” of being accepted by the EU. “I would vote for a deal, but this is not a deal,” she said.
Corbyn has dismissed Johnson’s plan as “Trump Deal Brexit” that would lower standards.
“It’s already clear that Johnson’s proposal would slash food safety and standards, exposing us to – among other things - chlorine-washed chicken and hormone-treated beef, currently banned under EU standards,” he said.
“And on environmental protections, Johnson’s proposals would mean the UK ditching the highest standards on things like air pollution or chemical safety. So the Tories are proposing weakening our existing environmental standards at exactly the point where urgent action is needed to tackle the climate emergency.”
A Commons victory could in theory strengthen Johnson’s negotiating hand when it comes to persuading the EU to agree to his plan.
However his proposal has so far been met with a lukewarm response from the EU27.
But Irish PM Leo Varadkar offered a glimmer of hope to Johnson as he said a deal could be secured in the next two weeks, but cautioned the current proposals do not form the basis for “deeper negotiations”.