Labour’s Keir Starmer will demand that the government release its economic analysis of different trading relationships after Brexit within days after his party wins a binding vote in the House of Commons over the issue on Wednesday.

The Guardian understands that Conservative MPs have been told to abstain in the opposition day debate, which will see an archaic parliamentary process used to force ministers to hand over the papers.

That will deliver an automatic victory for Starmer and the Labour party, who are demanding that the Commons Brexit select committee and MPs be able to read economic forecasts of post-Brexit growth drawn up by officials.

The leaked analysis, which has been described as incomplete by the Brexit minister Steve Baker, who also claimed forecasts by officials were “always wrong”, shows that Britain would be worse off under three possible trading scenarios.

“If parliament does pass this motion without government opposition then it is a significant win for Labour and indeed democracy. On decisions as significant as Brexit, parliament is entitled to know the likely impact of the government’s approach and thus to hold it to account,” said Starmer.

“What we need now from the government is clarity about when the documents will be handed over and a guarantee they will be so in an unedited and unredacted form.”

He said Labour would not “tolerate a repeat of last year’s saga when ministers sought to sidestep the will of parliament”.

That row, over a series of papers analysing the impact of Brexit on different sectors, embarrassed the secretary of state, David Davis, who ultimately claimed the information did not exist in the form he had originally suggested.

Baker claimed that publishing the latest studies, while negotiations were ongoing, would damage the “national interest”. He and Theresa May said they would be made available to MPs when the final deal had been hammered down.



Moreover, the minister said the three options that had been modelled – a comprehensive free trade deal, single market access and no deal at all – did not include the government’s preferred option of the “most ambitious relationship possible”.



Quick Guide What are Brexit options now? Four scenarios Show Staying in the single market and customs union The UK could sign up to all the EU’s rules and regulations, staying in the single market – which provides free movement of goods, services and people – and the customs union, in which EU members agree tariffs on external states. Freedom of movement would continue and the UK would keep paying into the Brussels pot. We would continue to have unfettered access to EU trade, but the pledge to “take back control” of laws, borders and money would not have been fulfilled. This is an unlikely outcome and one that may be possible only by reversing the Brexit decision, after a second referendum or election. The Norway model Britain could follow Norway, which is in the single market, is subject to freedom of movement rules and pays a fee to Brussels – but is outside the customs union. That combination would tie Britain to EU regulations but allow it to sign trade deals of its own. A “Norway-minus” deal is more likely. That would see the UK leave the single market and customs union and end free movement of people. But Britain would align its rules and regulations with Brussels, hoping this would allow a greater degree of market access. The UK would still be subject to EU rules. The Canada deal A comprehensive trade deal like the one handed to Canada would help British traders, as it would lower or eliminate tariffs. But there would be little on offer for the UK services industry. It is a bad outcome for financial services. Such a deal would leave Britain free to diverge from EU rules and regulations but that in turn would lead to border checks and the rise of other “non-tariff barriers” to trade. It would leave Britain free to forge new trade deals with other nations. Many in Brussels see this as a likely outcome, based on Theresa May’s direction so far. No deal Britain leaves with no trade deal, meaning that all trade is governed by World Trade Organization rules. Tariffs would be high, queues at the border long and the Irish border issue severe. In the short term, British aircraft might be unable to fly to some European destinations. The UK would quickly need to establish bilateral agreements to deal with the consequences, but the country would be free to take whatever future direction it wishes. It may need to deregulate to attract international business – a very different future and a lot of disruption.

However, the decision by Tories not to oppose Wednesday’s vote could be critical in forcing the government to hand over the information. Starmer is using a humble address – an ancient parliamentary method that makes a vote binding.

The Speaker, John Bercow, made clear last year that he would expect ministers to comply with such a vote. The motion does not include a timeline but Starmer will call for the information to be made available within days.