Labour will launch an attempt to force ministers to publish the government’s legal advice on Theresa May’s Irish backstop plan before any Brexit deal is put before parliament.

The shadow Brexit secretary, Keir Starmer, will on Tuesday use the humble address – an ancient procedure used by the party last year to force the release of Brexit impact assessments – to demand the government produce the backstop papers for scrutiny.

UK all but gives up on November Brexit summit Read more

He said the party would be using its opposition day debate to stage a vote on the motion as it would be untenable to keep MPs “in the dark” on the legal advice before asking them to vote on the prime minister’s Brexit plan.

The environment secretary, Michael Gove, has led cabinet calls for ministers to receive detailed information about the full legal advice given to May on her backstop plan for avoiding a hard border. Hard Brexit Tory MPs, as well as the DUP and the Liberal Democrats, have called for parliament to be given a full version.

However, government sources had doubts over whether the legal advice actually existed in written form, suggesting that the attorney general, Geoffrey Cox, would only update his draft once the deal was ready to be presented to cabinet, possibly later this week depending on negotiations in Brussels.

It has raised the prospect of ministers telling MPs they have nothing to produce, although Labour sources claimed its motion would be worded in such a way that the government would have to comply with the demand, even if at a later date.

Labour insiders predicted that the humble address would increase the pressure on the prime minister, almost certainly deepening schisms over Brexit in her own party as well.

Starmer said: “It’s simply untenable for the government to put forward any Brexit deal to parliament without providing the legal advice on what’s been agreed. At this critical stage, MPs can’t be kept in the dark nor can we risk parliament being bounced into a decision without having all of the facts available. Ministers should accept this motion and allow MPs to have an informed debate about the UK’s future relationship with the EU after Brexit.”

He said the UK’s departure from the EU could still be halted, contradicting his party’s leader, Jeremy Corbyn, who angered Labour MPs and supporters last week when he said Brexit could not be stopped.

Labour MPs criticise Corbyn for saying 'we can't stop' Brexit Read more

“Brexit can be stopped, but the real question is what are the decisions we are going to face over the next few weeks and months,” Starmer said.

He later added: “I’m not going to pretend there aren’t different views in the Labour party. That wouldn’t be real. But that’s why we worked so hard to say what is the common ground, what is it that we, as the Labour party, can all agree on for the way forward.”

Starmer said a possible second referendum was the agreed party policy. “This was a big issue at our party conference in September, and we had a very strong policy position that was endorsed by everybody – myself, Jeremy, Emily [Thornberry, the shadow foreign secretary] – the whole of the membership,” he said.

Corbyn ruled out backing a second referendum when asked on Saturday whether he agreed with the former Conservative minister Jo Johnson, who quit over Brexit last week, demanding a fresh vote. In an interview with Der Spiegel, Corbyn had already ruled out backing the idea: “Not really, no. The referendum took place.”

Labour has reached an uneasy internal truce on Brexit after members who supported remain left open the possibility of backing a second referendum if it could not force a general election.

However, Corbyn and his senior shadow ministers have long held more Eurosceptic views, with deep concerns over state aid rules among other issues, while two-thirds of Labour MPs represent seats that backed leave at the referendum.

Starmer said given the scale of the crisis, and the likelihood of delays scuppering the chances of another emergency EU summit, all options should be kept open. He dismissed the idea of Labour helping May get a deal through parliament.

Gordon Brown backs calls for second Brexit referendum Read more

“The national interest is getting the right deal,” he told Sky News. “One has to ask the question: is the prime minister genuinely negotiating in the national interest, or is she negotiating what she thinks she can get past her cabinet? And I think everybody knows the answer to that question.”

The shadow Brexit secretary said even if MPs were presented with an official option of accepting May’s plan or leaving without a deal, parliament would have some leeway: “If there was a motion that 400-plus MPs supported, saying we do not countenance no deal, and a minority countenanced no deal, the PM would then have to go forward in the teeth of parliament.”

He described the possible sequence of events. “We’ll look at the deal and vote it down if it doesn’t meet our tests,” Starmer said. “If that happens, we will call for a general election. If that doesn’t happen, then all options must remain on the table. That includes the option of a public vote.”