Will Britain’s next prime minister reverse Brexit?

This was already going to be a week of reflection on the legacy of Brexit. The referendum in which British voters shocked the world by narrowly opting to leave the European Union took place 10 years ago this Tuesday. But it’s become more of a live issue with British Prime Minister Keir Starmer’s announcement that he is stepping down, setting up a contest within the ruling Labour party to succeed him.

Starmer was elected in a landslide just two years ago, but his approval ratings are now more than 50 points underwater. There are a number of reasons for that, including sluggish economic growth, several damaging policy U-turns, and the controversial appointment of Jeffrey Epstein crony Peter Mandelson. But given that Starmer is Britain’s sixth prime minister in the past 10 years, it’s hard to avoid the impression that it’s become nearly impossible for anyone to govern the country successfully in the post-Brexit era. Every prime minister since the referendum has struggled either with figuring out how to implement Brexit or how to cope with the mostly disappointing economic and social results of it.

So, it’s not that surprising to see that many in the country are looking to turn the page on this era. Fifty-five percent of Britons favor returning to full membership in the EU, according to a recent YouGov poll. Perhaps, more notably, a recent European Council on Foreign Relations (ECFR) poll found that 63 percent favored closer economic relations with the EU, even if it meant accepting the freedom of movement of people between Britain and the continent — notable given how central arguments about border security were to the original case for Brexit and how the backlash to immigration has fueled the rise of the far-right Reform UK party.

While Starmer, though an opponent of Brexit, argued that there was no going back and that the Labour-led government had to make the best of it, Andy Burnham, the former mayor of Manchester, who is considered the front-runner to replace him, has said he would like to see the UK rejoin the EU in his lifetime — though he has also pledged not to “re-run” the debates over Brexit. Another top contender for the job, former health secretary Wes Streeting, also called for the UK to rejoin. A top Treasury official recently told Parliament that a return to membership was “an inevitability.” London Mayor Sadiq Khan has called for rejoining to be included in the Labour Party’s next election manifesto.

The idea is broadly popular on the other side of the Channel, too. Two thirds of EU citizens back the UK rejoining, according to the ECFR poll. Several European leaders have expressed support, as well.

Call it “Breenter,” “Brejoin,” or “Breturn” (there’s some debate about this). There’s clearly growing desire, or at least curiosity, about the idea of unwinding Brexit. But returning to the before times is probably easier said than done.

Polls show that strong majorities, even including supporters of the far-right Euroskeptic Reform UK, believe Brexit has had a negative impact on the country’s economy and their own finances. For a long time, it was difficult to disentangle the economic impact of Brexit from other recent shocks, including the COVID pandemic and the Russian invasion of Ukraine, but the picture is starting to get clearer. A recent Bank of England study estimated that the country’s GDP is between six and eight percent lower than it would have been if the UK had remained in the EU.

The impact is visible across the British economy: Productivity of British businesses and the scale of investment in the country are both down, and the rise in living standards since 2016 has been weak, relative to other nations. Ten years ago, Brexit supporters raised the specter of “Polish plumbers” stealing British jobs. Today, Poland looks like it could be wealthier than the UK in a few years. As for “taking back control” of the country’s borders, irregular migration to the UK has actually increased over the past decade.

Then, there’s the Trump factor. The US president supported Britain leaving back in 2016 and even once dubbed himself “Mr. Brexit.” During the referendum, advocates argued that leaving the EU would allow London to negotiate its own, more beneficial, free trade agreement with the United States. But talks over an agreement stalled. Last year’s “Economic Prosperity Deal” rolled back some of the tariffs imposed by President Donald Trump, but it falls far short of the comprehensive trade deal that was promised and was never ratified by Congress. That means the deal could be rolled back, either by this president or the next one.

Moreover, the often predatory approach this US administration has taken toward its allies has made the idea of the UK pooling its negotiating leverage with the EU seem more appealing than it did in 2016. That may become even more the case with emerging questions over the regulation of, and access to, cutting edge US-developed AI models. And efforts to bolster Europe’s military capacity and coordination in the wake of both Vladimir Putin’s Ukraine invasion and Trump’s undermining of NATO have been hampered by the fact that the UK and European countries are no longer part of one bloc. Taken together, EU membership may look a lot more appealing today to the Britons who voted and campaigned against it 10 years ago.

As a recent report from the think tank UK in a Changing Europe laid out, rejoining would likely require another mandate from the public. This could entail yet another referendum or a party — presumably Labour — running in a general election on a return platform. (Starmer’s successor will be chosen only by his party. The next general election isn’t scheduled until 2029, though the next prime minister could call one sooner.)

As Burnham’s comments indicated, given how bruising and divisive the Brexit fight was last time around, it’s far from clear whether the next prime minister — even if he or she supports returning to full membership — would want to use all their political capital on relitigating it.

Anand Menon, director of UK in a Changing Europe, said it’s difficult to imagine this happening without a “catastrophe” of some sort forcing the issue.

“If Labour are heading into the next election looking like they’re going to get slaughtered, they might think they need a roll of the dice to reunite the progressives,” he said. “Or if Donald Trump sends troops into Greenland, all bets are off.” (Indeed, Trump’s threat to Greenland is one reason why long-resistant Iceland is now moving quickly toward EU membership.)

If the UK did apply, there’s a formal, tried-and-true process by which countries apply for EU membership and their candidacies are assessed. Unlike some other prospective members, the UK, a member until recently, presumably wouldn’t have much trouble meeting criteria for rule of law, human rights, or economic openness.

But even so, the Union Jack almost certainly won’t be flying in Brussels again any time soon. The fastest accession process (Finland’s) took about three years. Britain’s candidacy would probably be dragged out longer, in part because European governments would want to be sure they really mean it this time. The rising political fortune of Nigel Farage’s Reform UK raises the prospect that a far-right British government could pull out of whatever deal a Labour one had negotiated. Britain’s membership would have to be approved by the parliaments of the other member states, and some countries, like France, would have to hold referendums of their own. It would take a while.

“Countries have very different views of Britain,” said Rosa Balfour, director of Carnegie Europe. “There are those that still think that the EU is better off without Britain. There are those who feel that Britain’s departure has really diminished the EU. Britain’s departure was very time consuming, and the wounds are still there.”

Britain is also unlikely to be able to get the same bespoke membership arrangement it had before. Even as an EU member, Britain opted out of using the euro as currency, out of joining the open border “Schengen area” that allows for free movement between member countries, and out of a variety of other economic and agricultural regulations. As Poland’s foreign minister recently put it, this time around, Britain would not get “à la carte” membership.

There are intermediate steps between the status quo and full membership that include a “Turkey-style” deal in which the UK would join a customs union with the EU, losing some control over its independent trade policy in the process, or a “Swiss-style” deal that would give the UK full access to the European market for goods and services but require accepting the free movement of people.

Whether a full return is actually “inevitable,” it’s clear that the country’s relationship with the EU is still a live issue, and that has implications not just for the UK itself but for the global economy, migration, and military competition.

Even reading about these terms may bring back some bad memories of the bruising and convoluted debate over Brexit and the long divorce talks that followed. Ultimately, though, events — including the rise of Trump, the war in Ukraine, COVID, and the emergence of AI — have changed the world, the fundamental question of just how much sovereignty Britain is willing to give up in order to access the benefits of integration with the EU still remains. The last six British prime ministers were unable to resolve that question. It’s a good bet the next one won’t either.