The European Union did not cause the 2007-08 financial crisis. The European Union did not instruct George Osborne to introduce an austerity policy which magnified the deleterious effects of that crisis. The European Union did not impose neoliberal and excessively deregulatory policies which contributed to a situation where the “fruits of globalisation” were concentrated in the top 5% of the population.

However, in a propaganda feat which will go down in history, the Leave campaigners managed to persuade enough British voters that the EU was the source of many of our problems, and, just as bizarrely, that leaving the EU would be the answer.

It was against the background of this farcical development that the Office for Budget Responsibility and the Treasury had to prepare the groundwork for last week’s autumn statement. Thanks to the combined impact of the financial crisis and the austerity programme, the OBR had already revised downwards its estimates of the country’s productivity and the growth of productive potential; this revision took place between last November’s autumn statement and the March budget.

Then came the referendum, and the net result of feverish work going on at the OBR since then is that the fallout from Brexit – indeed, from the very prospect of Brexit – is that the outlook for productivity growth has been revised downwards again, with all that this implies for living standards and the tax revenues that go to finance public spending.

One problem facing the OBR in making its assessment was that it had little idea what the government’s policy was for Brexit. This is not surprising, because the government itself has little idea either.

But Robert Chote and his colleagues at the OBR did not get where they are today without possessing a lot more sense and judgment that the Brexiters who have landed us in this mess. These are Brexiters who are so bereft of common sense that they argue departure from the EU will free this once-great nation to be able to trade with China, India, Australia and the rest of the world, as if we did not trade with them already.

Ah, they say, but freed from the constraints of the EU we shall be able to do even better. Tell that to Germany: an economy that, allegedly constrained by the EU, seems to fare a lot better in world markets than we do.

Now, one thing missing from the latest OBR report is the usual catchy soundbite we have come to expect: remember “economic rollercoaster”? I suspect the reason for the OBR’s more sober tone is that the facts, or lack of them, speak for themselves.

Thus the OBR states: “The OBR is required by legislation to produce its forecasts on the basis of current stated government policy (but not necessarily assuming that specific objectives will be met). In the current context of looming Brexit negotiations, this is far from straightforward.”

I’ll say! Notwithstanding the barrage of propaganda in the Brexit press that everything is fine and dandy with the post-referendum economy, the OBR knows something about economic time-lags. Furthermore, it does not commit the elementary error of assuming away the effects of something that has not yet happened – in other words, it does not confuse post-referendum with post-Brexit.

It says: “We have made a judgment – consistent with most external studies – that over the time horizon of our forecast [that is, the rest of this decade] any likely Brexit outcome would lead to lower trade flows, lower investment and lower net inward migration than we would otherwise have seen, and hence lower potential output.”

It points out that uncertainty will lead firms to delay investment, reducing economic growth, and the impact of that will be compounded as consumers are squeezed by higher import prices, thanks to the fall in the pound.

Now, as the chancellor pointed out in his speech to the Conservative party’s annual conference, the nation did not deliberately vote on 23 June to become poorer. But at the very least all the signs are that it will, via Brexit, become poorer than it otherwise would be. And thinktank after thinktank is telling us that it is the least well-off – many of whom apparently voted for Brexit as a protest – who are going to suffer most.

What is to be done? Well, Nicholas Boyle, emeritus professor of German at Cambridge University, has pointed out that only 28% of the population of this country voted to leave the EU. “Should 28% be entitled to compel 72% to do what they want?” he asks. That, he says, is the real constitutional issue.

“The 17 million [Leave voters] represented no one other than themselves. The members of the House of Commons represent all 64 million of us, whether voters or not.” He adds that if it is true that 70% of MPs do not wish to leave the European Union, then they “have every right to feel they more truly represent the views and interests of the country”.

Unfortunately, there is a timing problem. One suspects that when the true implications of Brexit become apparent in higher prices, squeezed incomes and an aggravation of austerity, large numbers of Leave voters will have second thoughts. The tragedy is that a lot of damage will have been done by then.