Downing Street will not block release of damning Brexit documents

Britain's Prime Minister Theresa May speaks during a meeting in 10 Downing Street this month. Picture: Getty Images

Downing Street said it would not resist a formal demand from Labour in the House of Commons to release forecasts showing that every available option for Brexit will damage economic growth.

The concession came just 12 hours after the Prime Minister told journalists accompanying her on a flight to China that publication of the report, dismissed as “partial” and “incomplete” by the government yesterday, would be wrong.

“When the time comes for parliament to vote on the final deal, we will ensure that parliament has the appropriate analysis on which to be fully informed, on which to base their judgment,” Mrs May said overnight.

“But it would be wrong to publish analysis before that analysis has been completed, and it would also be wrong to publish analysis which might prejudice our negotiating position.”

Papers prepared by the Department for Exiting the EU and obtained by website Buzzfeed suggested even with a comprehensive trade deal of the kind Mrs May is seeking, UK growth would be down by 5 per cent over the next 15 years.

Downing Street also said Justice Minister Phillip Lee had been called in by the chief whip after he tweeted if the figures in the leaked assessment were “anywhere near right”, there should be a “serious question” about the Government’s approach to Brexit.

This would rise to 8 per cent if Britain left without a deal and was forced to fall back on World Trade Organisation rules.

Downing Street made it clear Brexit-backing minister Steve Baker would not be reprimanded after telling MPs yesterday official forecasts drawn up by civil servants were “always wrong”. Asked why Mr Lee had been disciplined over his remarks but not the Brexit Minister, a spokesman said Mr Baker’s comments were made in a statement to the Commons, while Mr Lee had been “speculating” on leaked documents. A Government spokesman said of Mr Lee: “He has been spoken to by the chief whip and been reminded it is best to air views in private.”

The SNP’s Westminster leader Ian Blackford said the leaked analysis has sparked “chaos” in the government, claiming: “It’s now official government policy to do the wrong thing.”

Mr Blackford said: “[Mrs May] is struggling to keep her government together. We have got a Prime Minister who is weak, who is not providing any leadership, and never mind her party, her cabinet are at war with each other. It is an embarrassment.

“You cannot have a government minister publicly undermining the civil service. You are undermining the very foundations of government.”

The SNP MP added: “She is a Prime Minister that is massively out of her depth. I think that is becoming ever clearer.”