So far this week, the political news has been dominated by one issue: the European Union.

A large proportion of the Tory backbenches wrote to the prime minister urging him to give parliament full control of our laws. Business for Britain, the Eurosceptic campaign group, proposed radical changes to the way single market rules were enforced. George Osborne warned Brussels that if reform was rebuffed, Britain might well vote to leave.

This has been met on the left by eye-rolling – the Tories and other obsessives are banging on about Europe again. It is treated as an eternal mystery: why are the centre-right so worried about the EU?

The question ought to be reversed: why is the modern British left so relaxed, so enthusiastic even, about a project that clashes with socialist values in principle and in practice?

As a Conservative, I disagree with many of the tenets of socialism. But we are fortunate in this country to share democratic traditions on both sides of politics. From the civil war radicals to the chartists, from Keir Hardie to George Orwell, the heritage of British leftism is a democratic one.

So why are leftwing thinkers, politicians and activists today almost universally supportive of the EU, a fundamentally undemocratic project?

Run by an unelected executive-cum-civil-service, with a parliament that mostly functions only as a rubber stamp, the EU is deliberately arranged to pursue "ever closer union" through anti-democratic means. Even when its treaties require ratification by referendum it has a woeful record of ignoring negative responses.

There used to be a strong current of leftwing Euroscepticism in the UK, peaking with Michael Foot's commitment to leave the EEC. Trade unions and grassroots Labour supporters once rightly disliked the removal of power from the people – a route, as they saw it, to introduce capitalist policies without consent.

That democratic tradition was abandoned after Jacques Delors' speech to the TUC in 1988. He didn't make a pitch that their fears for democracy were wrong – instead, he effectively argued that Brussels' undemocratic machinery could be used to implement leftwing ideas without voters' consent. It was a shameful bargain to strike, but it was struck nonetheless.

We can disagree about whether the EU has been a socialist or capitalist influence – too much red tape or too much free market dogma, too much statist meddling or too much restriction on government deficits – but it is undeniable that it wields that influence without asking the people. Many of the outcomes of the European project ought to horrify the left, too.

Years of protectionism and subsidy for well-off European farmers have hobbled developing economies and literally starved poorer competitors around the world. The idiotic common fisheries policy played a major role in the ecological disaster engulfing North Sea fish stocks. Most recently, Greece has been brutally sacrificed in order to maintain the stability of a single currency that mainly benefits far wealthier countries in northern Europe.

And yet for some inexplicable reason the British left still embraces the EU, when by all logic and good sense they ought to be as Eurosceptic as their opponents on the right.

The prominent Eurosceptic voices today are almost universally those of the centre-right – not because it is a rightwing pursuit, but because the left has failed to uphold its own beliefs.

Most on the left would disagree with Tories and Ukip-ers on immigration, taxation, workplace regulation, green policies and everything else imaginable – but it should still follow that those issues ought to be decided democratically for ourselves, not undemocratically in Brussels.

With a renegotiation of where powers lie, and an in/out referendum likely to follow in 2017, we ought to see a return of that vanished beast: the leftwing Eurosceptic.