Brexit at 10: A Political Landscape Transformed
Ten years after the United Kingdom voted to leave the European Union, the political landscape has been reshaped beyond recognition. What began as a referendum on Europe has evolved into a prolonged era of political fragmentation, with smaller parties gaining ground and the traditional big two struggling to hold the centre. A series of reports from the Institute for Government, timed to mark the anniversary on 19 July 2026, track how Brexit unlocked long-term shifts in party membership, electoral behaviour, and governing coalitions. The evidence is stark: the era of two-party dominance is over, and a more fluid, unpredictable system has taken its place.
Andy Burnham, who became Labour leader after the 2024 general election, has made "new politics" the central theme of his leadership. In his first major speech as leader, Burnham explicitly linked the fragmentation to Brexit, arguing that the old tribal loyalties had been shattered by the referendum and never repaired. "The divide is not just between Leave and Remain anymore," he said. "It is between those who feel heard and those who feel left behind by every establishment party." That message resonates as smaller parties such as Reform UK, the Liberal Democrats, and the Greens have all posted record membership and vote shares in recent years.
The Numbers Behind the Fragmentation
The Institute for Government's three-part series – covering the Labour Party, the Conservative Party, and the broader trend of political fragmentation – paints a quantitative picture of the change. Party membership numbers, tracked since the 2016 referendum, show a dramatic fall in the combined membership of the Conservatives and Labour, even as overall political engagement has risen. In 2016, the two major parties accounted for roughly 80% of all party members in the UK. By 2026, that share has dropped below 50%. Smaller parties have absorbed the difference: Reform UK now claims over 120,000 members, the Liberal Democrats have stabilised at around 100,000, and the Greens have surged past 80,000.
The ECPR research, though its full text was not accessible, flagged how the availability of membership rights within parties has changed. Many smaller parties now offer easier online sign-up, lower fees, and more direct say in policy. That has attracted voters who once saw party membership as an exclusive, expensive club. Meanwhile, the Conservatives and Labour have both tightened internal rules, wary of entryism from opposing factions. The result: a system where joining a party is easier than ever – but loyalty is shorter-lived.
Andy Burnham's 'New Politics' Pitch
Andy Burnham's ascent to the Labour leadership was itself a product of the fragmentation. A former Labour minister and long-time mayor of Greater Manchester, Burnham positioned himself as the candidate who could reunite the party's warring Brexit factions. His "new politics" agenda goes beyond internal reform. It calls for proportional representation, a written constitution, and a directly elected upper house – all proposals that would further break the two-party mould. Burnham argues that the 2016 referendum exposed a broken political system, and that tinkering around the edges is no longer enough.
Critics within his own party warn that embracing proportional representation would permanently fragment the left, handing power to coalitions dominated by smaller parties. But Burnham counters that the fragmentation has already happened. "You cannot put the genie back in the bottle," he said in his speech. "The question is whether we build a system that reflects that new reality, or continue to pretend that it doesn't exist." His stance has won him support from former Liberal Democrat and Green voters, but it has also created friction with traditional Labour MPs who fear losing safe seats.
The By-Election That Sums Up a Decade
A single by-election held in the summer of 2026 crystallises the Balkanisation of British politics. In the normally safe Conservative seat of Wellingborough, a staggering 34 candidates appeared on the ballot – a record for any UK parliamentary contest. Among them was Nigel Farage, who after a brief retirement from frontline politics is seeking a return to Parliament as the Reform UK candidate. The field also included a Green, a Liberal Democrat, a Workers Party candidate, and independents representing local campaigns on potholes and hospital closures.
The sheer number of candidates made tactical voting almost impossible. Polls ahead of the vote showed Farage running strongly in second place, with the Conservative candidate struggling to hold on and Labour well back. The Liberal Democrats and Greens were splitting the Remain-leaning vote. Whatever the outcome, the by-election will be remembered as a symbol of how Brexit broke the mould: no party can assume a reliable base, and every election is now a free-for-all.
How the Conservative Party Lost Its Grip
The Institute for Government's report on the Conservative Party traces a decade of internal warfare after the 2016 referendum. The party has had five leaders since David Cameron resigned the morning after the result. Each leader tried to steer a different course on Brexit – from Theresa May's deal, to Boris Johnson's "Get Brexit Done", to Liz Truss's deregulation push, to Rishi Sunak's quiet consolidation. The instability alienated grassroots members and voters alike. By the 2024 general election, the Conservatives had haemorrhaged support to both Reform UK on the right and the Liberal Democrats in the centre.
Membership has fallen from a post-referendum peak of around 180,000 in 2019 to fewer than 100,000 in 2026. The party's base has aged dramatically; the average Conservative member is now over 65. Young voters, many of whom were not even eligible to vote in 2016, overwhelmingly back smaller parties or Labour under Burnham. The party's challenge is existential: can it ever win back the votes lost to Reform UK, or will the right of British politics remain permanently split?
Labour's Long Shadow from the Referendum
Labour's journey has been equally turbulent. Under Jeremy Corbyn, the party took a soft stance on Brexit that satisfied few. Keir Starmer, his successor, tried to rebuild credibility by taking a firm pro-European position, but that alienated many Leave-voting northern seats. Andy Burnham's election as leader in 2024 came on a platform of unity – a promise to respect both sides of the divide while pushing for systemic change. The Institute for Government's Labour report notes that the party's membership, while still the largest of any UK party, has been stagnant since 2019, with high turnover as Remain and Leave supporters clash internally.
Burnham's "new politics" gambit is a high-risk one. If he delivers on electoral reform, Labour could find itself in permanent coalition with smaller parties. If he fails, the fragmentation could accelerate, with the Liberal Democrats and Greens eating into Labour's urban strongholds. The next election, expected in 2029, will be the first test of whether his strategy can rebuild a progressive majority – or whether it merely speeds up the decline of the old order.
What's Next: A More Fragile, More Representative System?
Looking forward, the most likely scenario is that political fragmentation continues. The British Electoral System, first-past-the-post, was designed for two parties. It is now generating anomalous results: parties winning 15% of the vote can end up with single-digit seat shares, while others with 25% can win a near-majority of seats. Voter frustration with this disconnect will only grow. A coalition of small parties, including the Liberal Democrats, Greens, and possibly Reform UK, are already campaigning for a referendum on proportional representation. If Burnham's Labour supports that demand, the 2030s could see a wholesale change to how the UK votes.
That could mean more coalition governments, more by-elections like the one in Wellingborough, and more power shifting to smaller, single-issue parties. It would also mean the end of the stable two-party system that defined British politics for a century. Brexit lit the fuse; the fragmentation is the explosion. And ten years on, the dust is still settling.
For the major parties, the choice is stark: adapt to the new reality or face continued decline. The Conservatives must decide whether to merge with Reform UK or compete for the same shrinking pool of right-leaning voters. Labour must decide whether to embrace proportional representation or risk being overtaken by the Liberal Democrats as the main vehicle for progressive voters. Either way, the political map of the UK drawn in July 2026 looks very different from the one that existed in July 2016. And it will likely look different again by 2036.
