Theresa May is expected to publish 58 government studies on how Brexit will impact the economy after a self-imposed parliamentary defeat on a chaotic day in the House of Commons.
But the documents may not be published for three months and only in a redacted form.
For months the Tory government has refused to disclose the studies into how leaving the EU will hit various different industries, citing the risk of undermining its own negotiating stance with the EU.
The Labour opposition sought to force Mrs May’s hand on Wednesday by invoking an ancient parliamentary device designed to make the government hand over the papers — perhaps to a select committee.
Keir Starmer, shadow Brexit secretary, argued that if the Commons backed an opposition day motion on the issue then ministers would have to publish the information.
At a time of “huge anxiety and uncertainty”, it was important for the public to have sight of the potential impact of leaving the EU on British industry, he said. The motion was passed unanimously when the government abstained.
Labour found backing not only from prominent Europhile Tory MPs such as Anna Soubry, who said ministers were afraid they “might prick the golden balloon of the promised land of Brexit”. It was also backed by Eurosceptic Conservative Jacob Rees-Mogg, who said the government “must publish these papers in full”.
John Bercow, the Speaker, said after the vote he “expects” the government to respect the will of parliament and publish the assessments given that similar motions in the past have been “binding”.
Brexit minister Robin Walker had argued that the government would refuse to vote and then could simply ignore the vote if so inclined. The government has similarly abstained on several ODMs in recent weeks to avoid the possibility of outright defeat.
But Mr Walker later indicated that the government had not entirely ruled out publication: “I take note of the points made about looking at redaction and summary as an approach,” he told MPs
The government has given itself 12 weeks to respond.
Insiders at the Department for Exiting the European Union say the reports are unexciting. They describe them as “sectoral analysis” rather than impact assessment studies, considering issues such as exposure to EU regulations, reliance on European markets and possible alternative markets.
David Davis, Brexit secretary, downplayed the documents on Tuesday, telling MPs: “I would not over-estimate what they are.”
Mr Starmer had argued that blanket bans on the publication of government documents were “very rare”, with officials usually able to modify information in an acceptable way.
Meanwhile, Boris Johnson, foreign secretary, again went beyond official government policy on Brexit when he suggested the UK should leave all EU bodies that weren’t “purely intergovernmental”.
“My own feeling is that it would be very difficult for us to remain in any EU institution or any body” that entailed, for example, a role for the European Court of Justice or “any federal machinery”, he told MPs on Wednesday.
Ministers have not excluded the possibility that Britain could remain a member of some of European regulatory bodies, which have the ECJ as a backstop, while in some other policy areas such as data-sharing EU institutions are likely to be involved.