One would need to have been living under a rock not to know what the headline findings are from the Government’s internal economic modelling of Brexit scenarios.

All the outcomes – from departing with no trade deal, to staying in the single market – are projected to leave the British economy worse off relative to otherwise, according to last month’s well-publicised leak.

So Brexit, according to the Government’s own modelling, will do economic damage to the UK.

Yet the Government refuses to publish the underlying research, even though ministers have been forced to agree to make the document available to MPs within the confines of Parliament.

Apparently they believe publication would undermine the UK’s negotiating position with the rest of the European Union.

Why internal research that backs up what every other credible independent modelling exercise has found to be damaging is left to our imagination.

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And, in fact, the real reason for the publication refusal was identified by Damian Green in his first interview since his resignation this week.

“There’s a great problem of politicians who won’t accept evidence,” he told the BBC.

In other words, pro-Brexit ministers and the Brexit fundamentalists on the Tory backbenches don’t like the findings and so don’t want them to be released.

Green thinks his former ministerial colleagues should buck up and simply publish the work. “Let’s have this argument in public, that’s what democracies do,” he implored.

Perhaps the advice of technocratic experts is getting through. Did Green maybe hear Robert Chote, the head of the Government’s official spending watchdog, the Office for Budget Responsibility, who suggested earlier this month it had been a mistake to try to keep the work concealed in the first place.

Perhaps Green had an ear open when the Bank of England governor, Mark Carney, at his most recent press conference likewise suggested the work should be released “so there’s an as informed a debate as possible”.

Yet does publication actually matter now, given we already know the bottom-line results?

Damian Green attacks faith-based politics on Brexit

Beyond embarrassing those pro-Brexit ministers who informed us that leaving the EU would be a great economic fillip for the UK, is there anything to be gained from it?

The answer is yes.

As Paul Johnson, director of the Institute for Fiscal Studies, argues in an article for Prospect magazine, it’s less the precise numbers produced by such modelling exercises themselves than the general picture that really matters.

And the general picture has been that the vast majority of qualified trade economists are confident the UK will grow more slowly outside the single market and customs unions due to it being, by definition, more difficult to export to our biggest trading partners.

“Although not quite 100 per cent certain, these sorts of claims aren’t far off,” Johnson explains. “The exact impacts, on the other hand, are highly uncertain. In public debate, the inevitable arguments about the exact number somehow end up clouding the solid general conclusion.”

His reference to the “exact impacts” represents a powerful reason for full publication of this work.

The Brexit minister Steve Baker, one of those politicians who has a problem accepting evidence, recently dismissed economic forecasts as “always wrong”.

And many people, including some high-profile journalists, seem to believe the stronger-than-expected performance of the UK economy since the June 2016 Brexit vote has borne out the truth of this claim.

Yet they have failed to grasp the crucial fact that all the long-term Brexit impact projections have been “conditional”. That means they are predicated on certain assumptions about the behaviour of the economy independent of the impact of the factor (leaving the EU) they are trying to model.

The actual path of the economy will almost certainly be different to those sketched out because lots of other unpredictable things are happening to our economy. For instance, there may be stronger overseas demand for our exports as other countries experience an unanticipated boom, or perhaps, acting in the other direction, even weaker domestic productivity growth than feared. This can push overall GDP up or down relative to the conditional forecast.

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But it’s a basic error to conclude from this aggregate divergence that the assessment of the impact of the factor being studied – Brexit – was wrong.

There is a world of difference between unconditional and conditional economic forecasts. Many people, even those who would be shocked at the suggestion they are unwilling to accept evidence, clearly need to be educated in that distinction.

But it’s hard to learn a lesson when ministers keep their civil servants’ modelling assumptions secret and when the basic nature of the forecast – conditional or unconditional – itself remains under lock and key.