Jeremy Corbyn has invited senior politicians to a cross-party meeting to discuss “all tactics available” to prevent a no-deal Brexit.
The letter to opposition leaders and senior backbenchers said: “The country is heading into a constitutional and political storm, so it is vital that we meet urgently, before Parliament returns.
"The chaos and dislocation of Boris Johnson's no-deal Brexit is real and threatening, as the government's leaked Operation Yellowhammer dossier makes crystal clear. That's why we must do everything we can to stop it."
A Labour spokesperson said Mr Corbyn has "postponed international commitments to continue his push to block a damaging no-deal Brexit" - the Labour leader was expected to visit Ghana in West Africa next week.
The meeting is scheduled to take place on August 27 at 11am, one week before MPs return from recess to the House of Commons.
The Labour leader sent the invitation to Liberal Democrat leader Jo Swinson, SNP Westminster leader Ian Blackford, Plaid Cymru’s Liz Saville Roberts, Green Party MP Caroline Lucas and Change UK leader Anna Soubry.
Tory rebel MPs who oppose no deal are also copied in, including Guto Bebb, Dominic Grieve, Oliver Letwin and Caroline Spelman as well as former Conservative minister Nick Boles, who resigned the whip in opposition to the Government's approach to Brexit.
It follows a similar letter last week seeking support for Mr Corbyn’s plan to table a vote of no confidence in the government and take over as caretaker Prime Minister.
The proposal was met with mixed response; Ian Blackford welcomed the letter while Jo Swinson dismissed the idea of a Corbyn premiership as “nonsense”.