Labour MPs opposed to a second referendum are considering a “radical and dramatic intervention” to make clear to Jeremy Corbyn and Boris Johnson they are prepared to vote for a Brexit deal, with one estimating that dozens of colleagues are now ready to back the withdrawal agreement.

Stephen Kinnock, the Labour MP who coordinates around 30 MPs in a group called Respect the Result, said he believed that passing the withdrawal agreement was the most certain way of stopping the UK crashing out without a deal.

Kinnock, who had been urging Corbyn to do a deal with Theresa May in cross-party talks, said there was an increasing feeling among many of his colleagues opposed to a second referendum that passing the withdrawal agreement bill was the best option.

Despite Johnson’s refusal to negotiate with the EU unless it drops the backstop, Kinnock said a time would come in the autumn when a compromise deal could be done based on the withdrawal agreement that emerged out of cross-party talks.

“We’ve got to make a radical and dramatic intervention,” he said. “If enough of us do then it’s up to Boris Johnson to see where he goes from there. It means a large number of us going to see Jeremy and trying as hard as we possibly can telling him to make that big, bold offer, to face down the second referendum campaign and say there’s no time for that. We’ve got to get this deal over the line.

Len McCluskey: there is no path to a second Brexit referendum Read more

“And by the way, if it is the second referendum that you want then the only way you’re going to get it through a parliamentary route is having the opportunity to debate and vote on it at committee stage.

“If that doesn’t work then it’s perhaps a joint statement, a public gesture that says here are the 50 Labour MPs that would vote for this. You need to get 260 of your guys to vote for it and we can get it over the line. Then it’s a question of whether he can deliver it. I think Boris Johnson could lose about 50 of the hardliners. But I think he could gain 50 on our side.”

Kinnock said he believed a deal could potentially happen after MPs had tried to block no deal without cast-iron success. “Once it’s clear there is no parliamentary or legislative route to preventing no deal then the [withdrawal agreement bill] is the only game in town,” he said.

A number of Labour MPs, including Sarah Champion, Gareth Snell and Melanie Onn, have suggested they could now be prepare to back a deal in some circumstances, particularly if faced with the possibility of no deal. The Telegraph reported that Labour’s John Mann was a “go-between” with the government and some of those potentially willing to vote for a withdrawal deal.

“I think Boris will present a deal to parliament, roll something in glitter and get themselves over the line and a number of my colleagues would vote for that deal at that point,” one MP said. “Many of them are at a point now where they will take whatever is on the table, a second referendum is so divisive and no deal is so damaging.”

It is understood at least one Labour MP has consulted the House of Commons clerks about whether a backbencher could table something like an amendment to a motion that endorses the withdrawal agreement, by setting aside the requirement for parliament to agree the deal.

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It is unclear however, whether Tory MPs would be whipped to accept the previous deal in such circumstances, given how Johnson has railed against “the undemocratic backstop”.

Snell, who has abstained or opposed several motions designed to delay Brexit, said he and many other Labour MPs wanted the opportunity to vote for a deal, that he regretted not doing so in the spring and hoped Johnson would present a deal to parliament.

He said, however, that he would be prepared to give efforts to stop no deal a reasonable chance. “I want to stop no deal. My preference is still a deal but no deal would destroy Stoke. So I would grit my teeth and vote for mechanisms to stop no deal, but I want to know what they are working towards,” he said. “People asking us to vote to stop no deal cannot ask us to keep doing it blindly for every madcap scheme.”

Snell said he was concerned Johnson would not respect the views or mandate of parliament in the way Theresa May had done. Government sources have suggested they believe that even if Johnson was compelled to request an extension, there would be no way MPs could force him to do so.

“Yes, you can pass a bill to mandate the PM to ask for an extension to article 50 but you cannot legislate for sincerity. We could compel Boris Johnson to ask for an extension but we cannot stop him making it impossible for the EU to grant one,” Snell said.

Some MPs remain sceptical about parliamentary devices designed to delay Brexit in order to prevent no deal. The former Labour MP Ian Austin, who voted for May’s deal and later quit the party over its antisemitism crisis, said MPs would only be delaying an inevitable choice.

“I voted for a deal because I thought it was the best way of avoiding no deal and because the only result of Theresa May having to leave was a harder Brexit,” Austin said. “This is displacement activity. People can pretend there is a clever procedural device that makes it all go away, but in the end they are going to have to face up to their responsibilities and make a decision. They need to understand that there isn’t some parliamentary device that means they can keep avoiding the question.”

The move by the Labour MPs comes as the Unite leader Len McCluskey said Labour must support a pragmatic Brexit deal, arguing it appeared to be impossible to stop no deal and that there was no path to a second referendum.

The trade union boss, a key ally of Corbyn, said Labour had to address how it would approach negotiating future trade deals if the UK had left the EU after Labour came to power.

Senior figures from other trade unions privately expressed disappointment at McCluskey’s intervention, with one saying it was not sticking to the “agreed position” and it sounded like he had “spoken out of turn again”.