Polls suggest false claims about the cost of EU membership are now widely believed

A Leave victory would be a defeat for facts, truth and reason

"Reality has a well-known liberal bias," US comedian Stephen Colbert once joked. Never has that been more true than in this referendum campaign.

A series of polls this week revealed an astonishing chasm between those backing Leave and the facts. Polling by Ipsos Mori found that false claims by the Leave campaign that the EU costs the UK £350 million a week are widely believed as are equally false claims that Turkey are about to become a member. Overall, more voters believed invented claims about the cost of EU membership than those who believed the overwhelming consensus among experts about the negative impact of Brexit on the economy.

Other polls have also shown a worrying disconnect between public perception of the EU and the reality. Voters typically massively overestimate the number of EU migrants living in the UK, their use of benefits and the wider cost of our membership.

Of course voters being misinformed is nothing new, but what is far more worrying is the growing disdain in the UK for the very concept of facts themselves.

A startling poll this week found that while Remain voters generally trust statements by academics, economists, business leaders, international organisations and other experts, Leave voters basically trust nobody. Amazingly, pollsters YouGov failed to find a single group of experts which Leave voters were willing to trust. It seems that Michael Gove's claim that people "have had enough of experts" is more true than even he realised.

This is all deeply worrying for those who still hope that repeated expert warnings about the potential impact of Brexit on the economy will finally break through with voters. However, it is equally worrying for all those who also believe in the very concept of using facts and evidence in politics. If Leave wins next week, it would not only be a major blow to pro-Europeans, it would be an even bigger blow to the concepts of rational belief and evidence. It's not just the future of Britain's relationship with the EU which is at stake – it's the founding elements of the Enlightenment.

On the left there are still significant numbers of people who believe that Brexit will somehow benefit the left cause. In fact even within the Labour leadership there are those who privately believe that a vote to Leave will fatally divide the Tories and lead to Labour's resurgence. This is wildly misguided.

In reality a victory for Leave would be the biggest win for the hard right of British politics for decades. In one swift move, the most regressive voices in the country would be handed the authority to shift Britain in an irreversibly rightwards direction.

Not only would it be a victory for all the most anti-immigration voices in the country, it would also be a mandate to roll back all of the most progressive rights currently enjoyed by UK workers. It is no accident that some of the biggest advocates for Leave are the same people who most passionately fought against the extension of maternity and paternity rights and the minimum wage. When the Leave campaign say Brexit is a chance to "take back control" they don't often add who that control will be handed to, or indeed what they would do with it.

Of course the Remainers haven't quite lost yet but we're definitely at the straw-clutching end of the campaign. The latest poll of polls put Leave four points ahead, with some suggesting they could even be as much as six or 10 points clear.

The most optimistic Remainers point to the historical tendency for undecided voters to switch to the status quo in the final days of previous UK referendums. Others suggest that the masses of low-income and low-education voters who are backing Leave in big numbers, simply won't turn out on the day. Others simply refuse to believe the polls. After all, they all got it badly wrong in 2015. Could the same be about to happen again?

Maybe so. But with the British public apparently so resistant to facts and the people whose job it is to deal in those facts so mistrusted, there does not seem to be overwhelming cause for optimism.

Even if Remain do somehow scrape a narrow win on Thursday, there should be little cause for joy on the left. Whatever the result next week, this referendum campaign should strike real terror into the hearts of all those on the progressive side of British politics.

If the UK does indeed vote for Brexit then it will open the door to a dark new political era. And it will do so at the same time as the left's favourite weapons of facts, evidence and reason are less powerful than they have ever been before.

Adam Bienkov is the deputy editor of Politics.co.uk

The opinions in politics.co.uk's Comment and Analysis section are those of the author and are no reflection of the views of the website or its owners