Labour MP Lisa Nandy said there had been tentative conversations between Labour MPs and senior members of the cabinet in recent days – and revealed that around 40 rebels could defy Jeremy Corbyn to support a deal.
However, Ms Nandy warned that the prime minister’s new proposals were little more than a “pre-election party political broadcast”, arguing that he was “further away from achieving a deal” than two months ago.
It comes as Brexit secretary Steve Barclay revealed the government was “considering” a Commons vote on the new proposals ahead of the European Council summit on 17 October, to send a message to Brussels that Mr Johnson had the backing of MPs.
Ms Nandy told Sky News’ Ridge on Sunday: “I think there are a lot of Labour MPs, there are about 40 still, who have been working cross-party over the past three years trying to find a way to achieve a deal and there are still discussions going on.
“There’s a cross-party group, MPs for a deal. We’ve had some limited conversations with senior members of Boris Johnson’s government about what would be acceptable and how we might achieve that.”
The Wigan MP, whose constituency backed Leave in the referendum, said she was ready to back a deal but the prime minister’s plans fell short.
She said: “What we’ve got is a proposal which stands virtually no chance of being accepted by the EU which creates two borders on the island of Ireland which is completely incompatible with existing international law and which rips up the workers’ rights and protections and the environmental protections that we spent several months at the start of this year negotiating with the former prime minister.
“I would vote for a deal, but this is not a deal. This is a pre-election party-political broadcast from the prime minister, and the truth is that for all of the talk about getting Brexit done, we are further away from achieving a deal than we were two months ago when he became prime minister.”
Mr Barclay confirmed the government was holding talks with opposition MPs in a bid to secure their backing for a deal.
He told the Andrew Marr Show: “We are talking to members of parliament across the House because I think many members of parliament want to avoid no-deal.
“And particularly those members of parliament in Leave constituencies who have voted against no-deal and voted against a deal three times, then they will need to be able to address this issue when they return to their electorate.”
Asked if the government would hold a vote on the plans before the EU Council summit, Mr Barclay said: “We are considering it.”
Labour leavers have long been seen by the government as a key part of securing Commons support for any Brexit deal – but despite speculation that around 30 MPs could support Theresa May’s deal, only a handful actually rebelled.
Mr Johnson claimed he had been encouraged to discover not all MPs are “so recalcitrant” in supporting his plans.
“MPs from every wing of my own Conservative Party, from Northern Ireland’s DUP, even from Jeremy Corbyn’s own ranks, have said that our proposed deal looks like one they can get behind,” he wrote in the Sun on Sunday.
“Where the previous withdrawal agreement, backstop and all, drove an almighty wedge through the heart of parliament, I have heard positive noises from across the House.”