Jeremy Corbyn has been accused by opposition parties of favouring an alternative Brexit over a second referendum which could end with Britain staying in the EU.
The Labour leader has held meetings with opposition backers of a so-called People’s Vote, as well as a cross-party group of MPs pushing a softer Norway-style Brexit known as Common Market 2.0, to try to plot a course through the impasse in Westminster.
Following the first meeting, Labour called on other parties to “engage constructively” in finding an alternative Brexit deal if May’s deal or a second referendum do not have enough support in the Commons.
A spokesman meanwhile described the meeting with backers of a soft Brexit, including senior Tories Sir Oliver Letwin and Nick Boles, alongside Labour’s Stephen Kinnock and Lucy Powell, as “positive and detailed”.
But Corbyn faced a backlash from the SNP, Liberal Democrats, Plaid Cymru and the Green Party, who accused him of prevaricating over whether to back a second referendum.
Labour is split on a so-called People’s Vote and Corbyn has been backing both another vote and a softer Brexit as alternatives to Theresa May’s deal as a way of holding his party together.
But in a joint statement, the leaders of the smaller opposition parties said: “There is no such thing as a good Brexit – whether it is a Labour or Conservative version of it – jobs, public services and the environment will suffer.
“Remaining in the EU is the best deal on offer and with time running out, Labour must now deliver on their promises so that we can avoid a catastrophic Brexit.
“We hope that we can now work collaboratively and move swiftly to ensure the best possible chance for a fresh referendum to take place.”
One of the leaders, Lib Dem Sir Vince Cable, meanwhile suggested May was more likely to back a soft Brexit than Corbyn.
“I do think that is the case, it is a crazy situation but unfortunately that’s where we are,” he said.
Later, after the meeting to discuss Common Market 2.0, Kinnock suggested Labour was moving closer to backing the plan, which is closely aligned with the party’s stated desire for a permanent customs union and a close single market relationship.
“I really don’t want to tempt fate but I think there is a clear realisation in the leader’s office and I hope across our shadow cabinet that our proposal puts flesh on the bones of what it has already proposed,” he said.
One of the key factors is that the proposals enjoy “pretty substantial Conservative support” that will be unlocked once May’s deal is defeated again and could find a majority in the Commons, Kinnock said.
“Where we see that support coming from is the group of Conservatives who consistently vote for Theresa May’s deal, so we of course have to wait for Theresa May’s deal to be dealt with and for the final nail to be driven into the coffin.
“It’s then we think we can release the latent support there is on Conservative benches.”
The meeting came as EU chief negotiator Michel Barnier suggested there was a compromise to be made on a softer Brexit.
“I recall this political declaration which sets out the framework for our future could be made more ambitious in the coming days if a majority in the House of Commons so wish,” he said.
A Labour spokesman said of the meeting: “This afternoon, Jeremy Corbyn had positive and detailed discussions with Nick Boles, Oliver Letwin, Lucy Powell and Stephen Kinnock, supporters of the Common Market 2.0 model of a close economic relationship with the EU.
“All participants pledged to work together and with others across parliament to find a Commons majority for a close economic relationship with the EU to break the Brexit impasse and bring the country together.
“They discussed how to build greater support on areas of agreement between Labour’s alternative plan and Common Market 2.0 and find possible areas of compromise.”