A ‘Remain alliance’ pact that would see Labour stand aside for rival parties in some areas is backed by the overwhelming majority of its pro-EU supporters.
A poll of members of Remain Labour - a grassroots pro-EU group - found that 97% of them support Jeremy Corbyn making a deal with parties like the Lib Dems and SNP should Boris Johnson trigger a snap general election this autumn.
Such a pact would involve Labour standing candidates down in constituencies where the Lib Dems, SNP, Greens of Plaid Cymru have a better chance of defeating the Tory or Brexit Party candidate.
An equally large majority of the group - 95% - said if rebel Tories were not prepared to install Corbyn as caretaker prime minister in an anti- no-deal Brexit national unity government, Labour MPs should put aside tribal loyalty and throw their weight behind someone else, such as Lib Dem leader Jo Swinson or Conservative Remain stalwart Ken Clarke.
Andrew Lewin, founder of the Remain Labour campaign group said the “emphatic result” of the poll - which surveyed 1,000 members and supporters - showed the party’s rank and file wanted Corbyn to put “the national interest first” in order to avoid no-deal.
He said: “They expect the party leadership to do everything possible to stop a no-deal Brexit and are willing to form alliances with smaller parties to try to ensure the next parliament has a Remain majority.
“If a Remain alliance is going to succeed in a snap general election, the Labour Party has to lead it.
“If the pro-Remain parties fail to work together, the only winners will be Johnson and Farage. The losers will be the poorest and most vulnerable in our society, who will be hardest hit by Brexit.”
Just over 1,000 people were polled online, with 600 of them Labour party members and the rest Labour supporters.
The chances of the UK crashing out of the European Union without a deal on October 31 have increased dramatically since Johnson was crowned PM.
The government has ramped up no-deal preparations and Johnson, who was in Berlin to meet German Chancellor Angela Merkel on Wednesday, remains at loggerheads with EU leaders over the Northern Irish customs backstop.
But while a pro-Remain alliance is favoured by Swinson and leaders of other small parties, there is little prospect it would get off the ground because Corbyn is likely to pledge at the next election that he will negotiate a “Labour Brexit deal”.
Corbyn has backed holding a second referendum should Labour win the next general election.
As it stands, Labour could ask its voters to get behind its renegotiated Brexit deal in any new plebiscite - a strategy which is dividing the leadership - rather Remain, which was its official stance in the 2016 referendum.
Shadow cabinet figures, including Tom Watson, Diane Abbott, John McDonnell and Emily Thornberry, have broken ranks to reveal they would campaign for Remain over any Labour Brexit deal.
It is also unclear whether Johnson will plump for a snap general election pre-Brexit, with much depending on last-minute talks with Brussels.
If new attempts at a renegotiation fail, however, and the country is headed for a no-deal Brexit, Corbyn has said he will table a vote of no-confidence in Johnson, which, if successful, may force his hand.
No-deal opponents could also attempt to wrest control of the parliamentary agenda in order to pass legislation that would compel Johnson to seek an extension to Article 50.
On Wednesday, Corbyn invited fellow opposition leaders and senior MPs to a meeting, due to take place on Tuesday, to discuss how a cross-party alliance in the Commons could stop the UK from crashing out of the bloc.
He said: “The country is heading into a constitutional and political storm, so it is vital that we meet urgently, before parliament returns.”
Editor’s Note: This story has been amended to reflect the poll was a survey of Remain Labour supporters.