LONDON — On Wednesday, Britain’s prime minister, Theresa May, is to deliver a letter to the president of the European Council, Donald Tusk, informing him that after 44 years of membership, her nation is leaving the European Union. Approximately two years later, after negotiating the terms of that departure, the union will lose at a stroke “an eighth of its population, a sixth of its G.D.P., half its nuclear-arms cache and a seat on the U.N. Security Council,” as Susan Watkins, the editor of New Left Review, noted recently.

Ms. Watkins is a “Lexiteer,” as left-wing supporters of ‘Brexit’ like me are known. We were hardly a significant force among the 52 percent of Britons who voted to leave in the referendum of June 23. But we were an influence. A counterweight to the anti-immigrant fear mongering of the former leader of the right-wing U.K. Independence Party, Nigel Farage, Lexiteers argued a left-wing, democratic and internationalist case for Brexit. The position was expressed crisply by Perry Anderson, the former longtime editor of New Left Review: “The E.U. is now widely seen for what it has become: an oligarchic structure, riddled with corruption, built on a denial of any sort of popular sovereignty, enforcing a bitter economic regime of privilege for the few and duress for the many.”

Although Lexiteers have little patience for the national nihilism of “Davos Man,” the globalist elite, we are no xenophobes. We voted Leave because we believe it is essential to preserve the two things we value most: a democratic political system and a social-democratic society. We fear that the European Union’s authoritarian project of neoliberal integration is a breeding ground for the far right. By sealing off so much policy, including the imposition of long-term austerity measures and mass immigration, from the democratic process, the union has broken the contract between mainstream national politicians and their voters. This has opened the door to right-wing populists who claim to represent “the people,” already angry at austerity, against the immigrant.

It was the free-market economist Friedrich Hayek, the intellectual architect of neoliberalism, who called in 1939 for “interstate federalism” in Europe to prevent voters from using democracy to interfere with the operation of the free market. Simply put, as Jean-Claude Juncker, the president of the European Commission (the union’s executive body), did: “There can be no democratic choice against the European treaties.”