Labour is ready to work with rebel Tories to block a no-deal Brexit if Theresa May’s EU withdrawal plan fails, Sir Keir Starmer has said.

The shadow Brexit secretary was speaking to the Press Association shortly after John McDonnell raised the prospect of a “unity platform” across parties to protect jobs and the economy from being damaged by a chaotic departure from the EU.

Mr McDonnell suggested that Labour could secure a Commons majority for a compromise Brexit plan to avoid a “catastrophic” no-deal break with the EU.

Following the Prime Minister’s mauling in the Commons on Thursday, when MPs from all sides lined up to condemn her Brexit deal, both Mr McDonnell and Sir Kier said it was clear she could not get it through the House.

And Sir Keir said there would be “very, very choppy times” next week, when Mrs May’s survival as PM will be up for question.

Mrs May was effectively saying: “I’ve got a deal, it’s not very good”, he told PA in Gateshead.

“She’s not even selling it as good now, she’s just saying: ‘It’s better than leaving without one, I have brought back something pretty inadequate, if you don’t like that, you get even worse.’

“That is not a good enough choice, and it’s not just Labour and the opposition who is saying that, there are plenty of Conservative MPs who would not countenance us leaving without a deal and, I think, if it’s necessary, we will work together to stop no-deal happening.”

Mr McDonnell suggested Labour could seek support for an alternative agreement with the EU based on a permanent customs union and a “close collaborative relationship” with the single market.

John McDonnell interview
Shadow chancellor John McDonnell said a ‘unity platform’ against a no-deal Brexit was developing in Westminster (John Stillwell/PA)

“I think we can secure a majority. What is absolutely certain is that the Government’s proposal won’t command a majority in the House of Commons,” he told the BBC Radio 4 Today programme.

“Anyone having seen what happened in the House of Commons yesterday realises that the proposals that the Prime Minister brought forward will not command a majority and therefore there has to be some discussions. There has to be some movement.

“You saw in the debate yesterday, and certainly some of the discussions that have taken place around the House of Commons, people have looked over the edge of a no-deal Brexit and realised it could be catastrophic for our economy.

“I think our European partners also have looked over the edge of a no-deal Brexit and seen what an impact it could have on their economies.

“So I think what is emerging within the House of Commons now is almost a unity platform to avoid a no-deal, and therefore get down to serious discussions about what could construct a deal which would enable us to protect jobs and the economy.

“I think that is beginning to emerge around the permanency of the customs union, the relationship with the single market.”

The shadow chancellor said that when the Government of the day was unable to command a Commons majority, the constitutional convention was that the opposition should be invited to form an administration.

And he rejected claims that it was too late to re-open negotiations with Brussels on the terms of the withdrawal agreement.

“We have met (EU chief negotiator) Michel Barnier and others. If you can create the right atmosphere and relationship, there can be negotiations that are constructive,” he said.

“I think everyone realises the dangers that there are of a no-deal Brexit, both for the UK but also for Europe itself. I think there is a sense of urgency now about getting on with a proper negotiation.”