What miserable terrain we’re stuck in, post-Brexit vote, as the free trade v. free movement argument is endlessly discussed. Round and round we go, warning that leaving the single market and slapping more controls – we already have plenty – on immigration would harm the economy, but insisting that the public wants one, or both, or neither; who really knows?

As far as we can tell from polling, there is support both for remaining in the single market and for controls on immigration. We know that we can’t have free trade without free movement, because the EU keeps telling us so, even as ministers pretend that we can. More polling shows the public evenly split as to which is more important – controlling migration or free trade with the EU.

The Conservatives, who made unfulfillable promises about reducing net migration, are now saying that people who worry about immigration are having their concerns dismissed by a patronising, wealthy elite. The centre-left meanwhile fears that Labour strongholds will swing to the right unless the party promises to tackle free movement. Some Labour MPs have gone as far as claiming that immigration could cause racism or lead to riots. Apart from the victim-blaming, and the clearing of political ground for the populist right to build on, the claim doesn’t even make sense: there is less racism in more diverse parts of Britain.

But the idea persists that it would be undemocratic not to hear the demands to ‘control migration’ that were apparently written into every cross on every leave ballot. It would be elitist to privilege trade over migration controls – we’d be listening to the bankers and not the British people if we did that. It isn’t enough to honour the democratic vote to leave the EU; we have to honour it in a migrant-bashing, economy-stunting manner, for it to count at all.

To resist such a position isn’t to deny Westminster’s decades of neglecting the grinding hardship experienced across swaths of Britain: stagnating wages, insecure work, spiralling costs, a chronic lack of affordable housing, unbearable strain on the NHS. But if a politician says that any of these problems is caused by too much immigration, then they are lying. Migrants pay more in tax than they take in benefits and have little effect, either up or down, on wages. Study after study has shown that migrants don’t strain the housing market or public services.

The Conservatives know all this – they admitted as much. When David Cameron, ahead of the EU referendum, tried to negotiate a better deal on migration, his team could not find any ‘hard evidence’ that current levels of migration are adversely affecting communities in Britain. But in the face of these facts, what’s a Europhobic Tory to do? Admit that the hardship is caused not by migration but by deliberate government policy? Better find a scapegoat instead.

This is the challenge facing the progressive left. Now more than ever, it’s the job of the left to trust that the majority of the population is not racist, and move away from the notion that more immigration controls are necessary, possible or desirable. The progressive response to a populist right-wing surge is to take away their fuel – fight to alleviate the economic pain it thrives on, and reject the division it creates. When the new Ukip leader says he wants to replace Labour and make his party 'the patriotic voice of working people', the progressive line is to redirect the blame away from migrants and onto political decisions, to focus on fighting poverty and creating secure jobs, not to patronise people by suggesting everything can be made better with a bit of 'patriotism'. It's a hard line to take and will be met with ridicule and attack. But that's to be expected. That's what challenging a dominant political narrative looks like.

But if the left doesn’t hold a line, it enables the surge of nativist nationalism by conceding ground, allowing the debate to shift ever rightwards. Fo we really want to find out where it all ends? Do we really want to see how far right we can go?