Brexit: Government forced to publish secret legal advice after humiliating Commons defeat

The government will be forced to publish secret legal advice around its Brexit blueprint after cross-party MPs inflicted a humiliating defeat on the prime minister.

MPs backed a binding motion that obliges the government to share attorney general Geoffrey Cox’s guidance on the draft withdrawal agreement with Brussels, including the backstop plan to prevent a hard border in Ireland.

Ministers had hoped to keep the details under wraps, offering MPs only a summary of the opinion from its lawyers, but Labour argued that parliament must have all the facts before it can endorse Theresa May’s plan.

It comes as Downing Street confirmed a draft agreement had been reached with Brussels, which will be discussed at an emergency cabinet meeting on Wednesday.

David Lidington, the prime minister’s de facto deputy, tried to stave off a defeat by saying the government would lay out its position before MPs vote on the final deal.

But Conservative MPs were then forced to abstain on the motion rather than risk defeat from an unlikely alliance of Labour, Tory Brexiteers and the Democratic Unionist Party (DUP) – which props up Ms May’s government.

DUP Brexit spokesman Sammy Wilson said his party would have voted with Labour, adding: “If we’re going to make a decision on this it’s a most important decision, then we should know the full implications.

“It should be spelt out to the public – the people of Northern Ireland and the people of the UK should know, is the government binding you to an arrangement which will be impossible to get out of collectively or just for the people of Northern Ireland?”

Labour sought to use an arcane parliamentary device called a “humble address” to access the advice, which it previously used to uncover a string of damaging Brexit impact assessments.

Shadow Brexit secretary Sir Keir Starmer said: “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.”

Tory Brexiteers from the 60-strong European Research Group (ERG) also launched its own motion to secure the advice, as many Eurosceptic MPs fear being bounced into a deal that maintains close ties with Brussels.

The rival bid was not selected so the ERG MPs vowed to abstain on Labour’s motion – significantly bolstering their cause.

Mr Lidington conceded to “make available to all members of the house, following the conclusion of negotiations and ahead of the meaningful vote, a full, reasoned position statement laying out the government’s both political and also legal position on the proposed withdrawal agreement, and that includes any protocols that might be attached to it”.

He added: “In addition, the attorney general has authorised me to confirm to the house this afternoon that he is ready to assist further by making an oral statement to the house and to take questions from members of the house in the normal way.”

Tory MP Anna Soubry said she had been told to abstain on the vote, and accused the government of allowing Brexiteers to run the country.

Conservative former attorney general Dominic Grieve said publishing the legal advice would be a mistake but said ministers appeared to be setting a “quite disgraceful timetable” to “bulldoze” MPs into supporting the deal without enough information.