The coming years offer an unprecedented opportunity for the left. Or at least they ought to. The chances that a protracted Brexit will not result in a long period of economic stagnation are slim, especially now it looks certain the government is pursuing a "hard Brexit" which entails leaving the European single market.

A taste of things to come was offered by the car maker Nissan on Friday, when its chief executive Carlos Ghosn warned that the company would be deferring all new investment in its plant in the North East until it was clear whether or not Britain was leaving the single market – and whether, as a consequence, Nissan and other car manufacturers would face stiff tariffs of up to 10 per cent to export to the EU.

Nissan employs 7,000 workers at its plant in Sunderland. Other large employers will invariably be viewing the prospect of leaving the single market with similar trepidation. How many of them ultimately dump the British arms of their businesses is another question altogether, but it does seem likely that some will shed jobs if that's the price of securing their bottom line.

The apparent paradox at the heart of Theresa May's new government is that it is pursuing a hard-right course on Europe while at home softening its line on the economy. With respect to the second part of that equation, May has promised to govern on behalf of the "just managing" by "improving the security and rights of ordinary working people". The Tories have even tried to brand themselves the "workers' party" this week at conference. May's chancellor Philip Hammond has also abandoned George Osborne's fiscal target of balancing the books by 2020.

However this apparent paradox – between hard Brexit on Europe and a tilt at home toward what were once called the "left behind" classes – is not as unusual as it at first seems. Viewed together, the constituent parts of Theresa May's agenda sit comfortably with the overall direction of political travel in the West: away from the Thatcherite liberalism of the past 30 years and toward a more interventionist vision of the state. The Blairite-Cameroonian liberals who have been ubiquitous in recent years sound today like Charles Dickens's capitalist villains: bleating about "progress" while large numbers of people live in penury and toil away on sub-standard wages.

This provides an opening to a left which has grown accustomed to languishing in the political doldrums. There is a growing realisation across the political spectrum that class and wealth are important again. The Tories are moving onto Labour territory for reasons of pragmatism, but they also recognise that the wind is blowing in a different direction. The economic settlement of the late twentieth century is coming unstuck; Brexit was a kickback against economic as well as social liberalism; and left to its own devices the market has not lifted six million working households out of poverty.

Yet it is hard to see how Labour can make any inroads into Theresa May's majority while the party's view of the world beyond Britain is hamstrung by a politics which is as rotten as the corpse of Thatcherism.

The plague of anti-Semitism currently ravaging the Labour Party offers a lesson in the illusion of a clean separation between international and domestic policy. The Jackie Walkers of the party are just one consequence of the left's distorted view of the world beyond Britain. In a world in which the United States is evil incarnate, Israel is its colonial appendage. Existential opposition to the Jewish state is thus de rigour. Moreover, Israel's fealty to the United States robs the Jews of their status as victims, and because racism is supposedly only about power, Jews cannot be victims of racism in the same sense that other historically persecuted groups can. Combine this with the left's sense of overarching goodness and you end up with something close to what Dostoevsky termed the "right to dishonour" – left-wingers granting themselves permission to behave badly if it (in their mind) furthers the greater good.

Today in Venezuela tens of thousands of people are struggling to get hold of even the basics of life in the most oil-rich country in the world. Yet until recently Venezuela was the apple in the eye of the Corbynista left. Paeans to the country were churned out in liberal newspapers and members of the shadow cabinet were found praising the regime.

Similarly, after initially opposing the Iraq war, the Stop the War Coalition, which Corbyn has supported, went on to support the so-called "resistance" in that country – once known as Al-Qaeda in Iraq, today better known as ISIS. More recently the organisation has invited Assadists to speak at its events – because they are sufficiently anti-western – and blamed NATO for Russia's bloody invasion of Crimea. A left which believes that NATO is a greater threat to Western freedom than Vladimir Putin is not the vehicle for emancipation it believes itself to be. What Corbyn has called "one of the most important democratic campaigns of modern times" is currently led by Andrew Murray, an avowed Leninist who has previously pledged his "solidarity" with North Korea. Rumour has it that Murray is lined up to be the next general secretary of the Labour Party.

And so for all the talk about "twenty-first century socialism", the left is evidently still infected by some distinctly twentieth century habits of mind: lesser-evilism, authoritarianism and an anti-imperialism of fools which translates as apologia for groups like Hamas and the IRA. It is a politics which bans McDonalds from its party conference while providing space for the Cuba Solidarity Campaign. (And objecting to the latter is hardly right-wing: it was Leon Trotsky after all who noted that liberal democracy at least permits "isles of proletarian democracy". Or put another way, McDonalds grudgingly allows trade unions while the Castro regime throws their leaders in jail.)

There is an opening for the British left, and the Tory conference's new-found enthusiasm for the state demonstrates that. But Jeremy Corbyn's Labour is no threat to Theresa May – despite the new-found appetite for harnessing the market to social ends. When the Tory electoral machinery starts rolling – whether this year, next year or in 2020 – the left's foreign policy positions of recent years will cancel out any hearing it might get for its putative domestic radicalism.

This is not (regrettably) due to some mass public outpouring of internationalism. It is a question of patriotism but also of trust: if the Corbynistas have been so wrong about events far away, the public will rightly ask, how on earth can they be trusted to run things closer to home?

James Bloodworth is the author of The Myth of Meritocracy