Britain seems to be mired in a never-ending constipated debate about Brexit. We are discovering how interconnected the economy and society we inhabit is, and how difficult it is to disentangle the territory of the UK from the institutions and rules of the EU. Leaving the single market and the customs union could bring drastic economic consequences, as well as the possible breakup of the UK and the renewal of conflict in Northern Ireland. Yet a soft Brexit merely means that we will have no political say on how these institutions develop. And as our politicians spend most of their time tediously reminding us, there are many equally problematic variations between these two options.

These dilemmas are reflected in the contradictory position of the Labour party. In his much heralded Europe speech, Jeremy Corbyn favoured remaining in a customs union to preserve the free movement of goods and a soft border within Ireland, but rejected staying in the single market because of its neoliberal aspects.

And yet, it is membership of the single market that would preserve many of the progressive elements of EU membership: the free movement of people, and environmental and labour standards. The customs union, by contrast, is arguably the central plank of the neoliberal vision for Europe. Moreover, if we remain in a customs union while leaving the EU, we will have almost no political influence over the future of our interconnected economy and society, even if the EU agrees to consult the UK after Brexit, as Corbyn has suggested.

Play Video 3:35 Jeremy Corbyn: UK should remain in a customs union with EU – video

How do we escape from this depressing self-referential debate? We need to shift the narrative about why Labour needs to adopt a clear anti-Brexit stance – one that offers hope in place of Brexit fears. This is the argument of a new pamphlet published on Thursday, entitled The Corbyn Moment and European Socialism.

Instead of negative arguments about how bad the consequences of different versions of Brexit will be, let’s begin to talk about the extraordinary possibilities open to a Corbyn government inside the EU. In his speeches, Corbyn rightly emphasises the need to tax multinationals, to control the volatility of financial markets, address climate change and end global conflicts. But this is not something the UK can do on its own. It is only through the EU that it is possible to envisage seriously dealing with such global challenges.

There are pressures for reform inside the EU. President Emmanuel Macron is putting forward all kinds of proposals for reforming the eurozone; the new German coalition will have a Social Democrat finance minister; and a leftwing government in Portugal is proving that anti-austerity policies work. On the other hand, the rise of rightwing populism, especially in central Europe and Italy, is pulling in an opposite direction. With Labour’s sister parties in crisis and people crying out for new ideas, a Corbyn government could act as a catalyst for transformative change in Europe.

Corbyn’s recent Brexit speeches are a brave attempt to overcome the polarisation between leavers and remainers

It is worth remembering that the EU began as a peace project, designed to overcome Europe’s sorry history of fascism, imperialism and war. Many of its founders envisaged a united socialist Europe. It was successive British governments, starting with Margaret Thatcher, that contributed to creeping neoliberalism and acted as a brake on more progressive developments.

We need to reimagine the EU as a new kind of political institution capable of managing today’s interconnected economies and societies. We could think of it as a sort of model of global governance: closing tax havens for multinational companies, regulating global financial flows, or controlling carbon emissions – and overcoming inequality, bringing peace to conflict zones, managing migration and refugee flows, and constructing resource-saving infrastructure. Our pamphlet describes how this is beginning to happen and why a Corbyn government could make a huge positive difference.

The Brexit vote in Labour constituencies represented a rejection of the establishment. It was the expression of powerlessness and frustration that has accompanied de-industrialisation, growing inequality, and extreme austerity policies, all of which are associated with globalisation. Leaving the EU will not enable us to take back control; on the contrary, it will make us poorer and more powerless.

Tories seek legal advice on vote after Jeremy Corbyn backs customs union Read more

Instead of responding to the feelings of powerlessness and frustration by embracing Brexit, Labour needs to offer a realistic prospect of how to go beyond the status quo and address the everyday problems experienced in deprived areas. Ultimately, this can only be done at a European and a global level.

Corbyn’s recent Brexit speeches are a brave attempt to overcome the polarisation between leavers and remainers. But this polarisation cannot be overcome through compromise. Corbyn has already shifted the narrative on austerity, and is in the process of shifting the narrative on terrorism and the “war on terror”. Now, he must lead the debate again – and shift the narrative on Europe, not only in Britain, but across the continent.

• Mary Kaldor is professor of global governance at the London School of Economics and a member of Another Europe is Possible