Theresa May’s former deputy has warned that the UK is in danger of adopting “faith-based” Brexit policies if ministers ignore economic forecasts predicting a hit to the British economy.

Damian Green called for all economic forecasting of the UK’s withdrawal plans to be released and for the public to be allowed an open debate on how the country should proceed.

Whitehall documents recently predicted the UK would be worse off after withdrawal regardless of whether it secures an EU trade deal, sparking anger from Tory right-wingers who accused the civil service of trying to sabotage Brexit.

But in a move that threatens to lever open Conservative Brexit divisions ahead of a crunch cabinet meeting this week, Mr Green rejected their claims as “conspiracy theories”.

Speaking in a BBC interview to be broadcast this evening, he said: “There’s a great problem of politicians who won’t accept evidence.

“We can all argue about economic forecasts and none of them are 100 per cent accurate, but you have to some extent rely on them and if you reject evidence you don’t like, then you are likely to end up producing faith-based policies.

“There are politicians who would prefer not to have the evidence there.”

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The Government has been under intense pressure for months to publish official forecasts of Brexit’s impact on the economy, and have only released anything following votes in Parliament.

When a more recent analysis showed the UK would be worse of outside the EU after 15 years, regardless of whether it is still in the single market, has a trade deal or is on WTO trading terms, Ms May rebuffed the story by saying the document had not analysed the particular deal she was seeking.

She went on to pledge that Parliament would be given analysis of the final deal the UK agrees before it votes on the issue.

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Mr Green went on to say: “If analysis is being produced then publish it. And frankly there will be a big political debate ... let’s have this argument in public, that’s what democracies do.”

His interview with the BBC Radio 4 programme The Ministry of Leave will be broadcast at 8pm this evening, but has already sparked an angry reaction from politicians who backed Remain.

A Government spokesperson said: “The Department’s purpose is to negotiate our successful exit from the European Union, and therefore a significant amount of our work is sensitive. We always strive to balance our commitment to transparency with the need to protect sensitive information that could affect our negotiating position.

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“Throughout this process we have been as transparent as possible – as demonstrated by the number of speeches setting out our position by the Prime Minister and her Cabinet colleagues, as well as the 14 position papers we’ve published.”

Labour MP Stephen Doughty, a leading supporter of the Open Britain campaign, said: “The fact that even Theresa May’s former deputy, Damian Green, is saying that the Government should release their secret Brexit impact assessments for the public to see is a damning indictment of her behind-closed-doors, secretive approach to Brexit.”

Tom Brake, Liberal Democrat Brexit Spokesperson, said: “It is shameful that this government is keeping the public in the dark about Brexit.

“The future of the UK is being plotted behind closed doors, without scrutiny and without transparency.”