A day shy of the tenth anniversary of Britain’s vote to leave the European Union, its latest prime ministerial resignation looked, at first, like another Westminster personnel drama. But the deeper story is economic. Since the Brexit referendum of June 23, 2016, Britain has cycled through leaders at a pace that suggests not renewal but frustration: voters and parties keep demanding new management because the promised restoration of growth, control and competence keeps failing to arrive.
The churn is remarkable. Since the 2016 referendum, Britain has been led by David Cameron, Theresa May, Boris Johnson, Liz Truss, Rishi Sunak and Keir Starmer. Cameron resigned immediately after losing the referendum. May was consumed by the mechanics of withdrawal. Johnson won a large majority promising to “get Brexit done,” only to fall amid scandal and exhaustion. Truss lasted 49 days after markets rejected her fiscal experiment. Sunak inherited crisis management and could not prevent Conservative collapse. Starmer then arrived promising stability, competence and growth, but his own resignation less than two years after Labour’s landslide shows how quickly British politics now burns through authority. The issue is not simply that Britain has had weak leaders. It is that each leader has been asked to deliver a post-Brexit renewal that the economy has not supported.
The instability is visible not only in Downing Street but in the composition of Parliament itself. In 2015, before the Brexit vote, British politics still looked recognizably two-party: the Conservatives won 330 seats and Labour 232, while the SNP’s 56-seat surge was mostly confined to Scotland. Today, the Commons is far more fragmented beneath Labour’s headline majority. Labour remains dominant in seat terms, but the Conservatives have been reduced to a shadow of their 2015 position, the Liberal Democrats have revived, the SNP has fallen back, Reform UK has gained a parliamentary foothold, and independents are more visible. That churn matters because it shows how volatile the underlying electoral coalitions have become. Brexit did not simply rearrange Britain’s relationship with Europe; it scrambled the voter map at home, weakening old party loyalties and making governments look powerful one election and exhausted by the next.
The economic backdrop helps explain why the political system has become so unforgiving. Brexit did not create all of Britain’s weaknesses, but it added friction to an economy that already had too little momentum. By mid-2024, UK real GDP per head was still 0.6 percent below its pre-pandemic level even though total real GDP was 2.9 percent higher. That is the central political problem: Britain can grow in aggregate while many voters feel no improvement in living standards. The Office for Budget Responsibility assumes that Brexit will leave both imports and exports 15 percent lower than they would have been inside the EU and reduce long-run productivity by 4 percent. That is not a forecast of immediate collapse; it is a measure of lost capacity. A country can continue growing and still be poorer than it otherwise would have been.
Demographics sharpen the contradiction. Brexit was sold partly as a way to regain control of immigration, but it did not produce a lower-migration economy. It replaced one migration system with another. Before the referendum, EU citizens made up a majority of UK immigration and net migration. Since 2022, EU net migration has been negative, as the post-Brexit system reduced the ability and incentive for EU workers to move to Britain. But non-EU migration then surged under the visa-based system. Overall net migration reached a record 906,000 in the year to June 2023 before falling to 431,000 in 2024. The result left both sides dissatisfied: businesses still needed foreign workers, voters did not see the lower-immigration settlement many had expected, and faster population growth made weak GDP-per-head performance harder to ignore. Britain had taken back formal control, but control did not mean economic ease.
That is why Starmer’s resignation should be read as more than a judgment on one prime minister. Britain keeps changing leaders because it is still searching for a governing formula that can reconcile Brexit’s political promise with its economic consequences. Voters were told that leaving the EU would restore control and unlock a more dynamic national model. Instead, Britain has endured weaker trade intensity, poor productivity prospects, pressure on public services, an unsettled immigration model and repeated experiments in political management. The lesson extends beyond Britain. As we argued in our 2026 Outlook, nationalism, populism and protectionism can be politically powerful because they offer citizens a simple promise: more control, more sovereignty and better economic outcomes. But Britain was an early adopter of these policies, and its experience shows the risk. If countries, including the United States, continue down a similar path, they may find that protection and sovereignty do not automatically translate into stronger growth. Economies can stagnate relative to potential, citizens can become more dissatisfied with their leaders, and that dissatisfaction can feed the next round of political instability. Britain’s revolving door at Downing Street may therefore be less an outlier than a warning.
Ardavan Mobasheri
Chief Economist