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UK: Labour’s Wide Majority Pushing First Past the Post to Breaking Point

When the exit poll for the UK’s national parliament election was published showing centre-left Labour (S&D) winning a landslide majority, it appeared to be a victory rivalling Tony Blair’s 1997 and 2001 landslides. And certainly, in terms of the seat tally, the parliamentary delegation of 411 Labour MPs backing newly-appointed Prime Minister Keir Starmer constitutes an almost identical proportion of seats as those previous landslides.

Yet, as results were tallied, it became clear that Keir Starmer’s landslide differed from Tony Blair’s in one key respect. Whereas Tony Blair surpassed 400 seats on vote shares of 43.2% and then 40.7%, Keir Starmer’s Labour coalition ultimately comprised just 33.7% of the voters. This was a considerably lower vote share than expected; while Labour had lost ground during the election campaign, falling from 44% to 39% in our polling average, not a single poll had placed the party’s vote share this low.

No party has ever won a majority on such a low vote share before in the United Kingdom, let alone a majority of this size and scale. The previous record was Tony Blair’s 2005 victory with 35.2% of the vote, which ‘merely’ netted him 355 seats.

Three Keys to Labour Success

This remarkable result, securing 63.2% of seats on a vote share of just 33.7%, was achieved in several ways. First, the Conservative (~ ECR) vote collapse to 23.7%, while slightly ahead of the polling average, ensured a considerable lead for Labour even without needing to substantially grow their own vote. Under the first past the post system, vote leads in individual seats are more important than the total vote share. This is especially true for countries which are transitioning into genuinely multi-party systems, something which—for the moment at least—appears to be happening in the UK.

Labour was thereby able to sweep a number of seats on relatively low vote shares. Most dramatically, in South West Norfolk, Labour defeated former Conservative Prime Minister Liz Truss with a vote share of just 26.7%. In some parts of the UK Labour’s vote proved even more efficient. In Scotland, the party won 64.9% of seats on 35.3% of the vote with just a five point lead over its nearest challenger, the pro-independence Scottish National Party (G/EFA). In Wales, Labour won an astonishing 84.4% of seats on just 37.0% of the vote, benefitting from a total Conservative wipeout.

Secondly, Labour’s political strategy since 2019 has focused on producing a more electorally efficient vote. Though its final vote share of 33.7% is not much more impressive than 2019—and below the 40% achieved by former party leader Jeremy Corbyn in 2017—the party was able to assemble a voter coalition distributed much more efficiently to win seats. The party sacrificed inner-city and urban votes which had piled up during the Corbyn years to make gains in more electorally advantageous areas. This led to a small loss of seats to the Green Party of England and Wales (G/EFA) and some independents, including Corbyn himself, but these were offset by gains in Conservative seats across the country.

A quantitative political analyst, Chris Terry-Enescu, describes this as a strategy of ‘depolarisation,’ enabling Labour to make gains in traditional Conservative areas by making itself inoffensive enough to preclude the kind of polarisation which ensured sizable anti-Labour votes harnessed by the Conservative Party under Corbyn.

Finally, this election saw an upsurge in anti-Conservative tactical voting. There was no formal agreement between opposition parties but in practice Labour and the Liberal Democrats (RE) appear to have allocated resources and campaign efforts in a way which left each other alone in many of their respective target constituencies. Prior to the election, a YouGov poll found about one in five voters claimed to be voting tactically, with the highest numbers recorded among those intending to vote Labour and Liberal Democrat. The Labour vote may have been suppressed by higher than usual tactical voting—although this phenomenon also serves to reinforce the major parties’ vote shares in most seats.

Conversely, polling which showed Labour on course for a historic landslide—an expectation reinforced by Conservative messaging urging voters to block a Labour ‘supermajority’—may have encouraged some anti-Conservative voters to opt for their preferred option at the last moment, believing a Labour government was essentially guaranteed. Such a late movement is one potential explanation for why polls overestimated Labour’s ultimate vote share.

The Most Disproportionate Election in History

As a result, the UK experienced one of the most disproportionate election results in its history, with an unprecedented mismatch between the share of votes cast and share of seats won. Using the Gallagher Index, which measures the proportionality of elections on a scale from 0 to 100, the 2024 national parliament election scores 24.0, a record high since at least the Second World War. This surpasses the 20.6 registered in 1983 and is well above the score of 11.8 recorded at the last election. For reference, no other national parliament in Europe registers a score higher than 13 on the Gallagher Index.

We can understand the extent of the election’s disproportionality by breaking down how many votes were cast for each seat won by a party. In the below chart, we can see Labour had the most electorally efficient vote, electing an MP for every 23,612 votes it received. At the far end of the scale, the UK’s combined Green parties (G/EFA) received 485,816 votes for each seat they received, while right-wing Reform UK (~NI) received a staggering 823,444 votes for each seat it won.

According to the Electoral Reform Society, 57.8% of voters have no representation by a party or candidate they voted for. Or to put it another way, we could have shredded over half the ballots cast in this election and the result would be entirely unchanged.

No Reform on the Horizon

Consequently, there has been increased discussion of electoral reform in the UK. Reform UK has published graphics arguing ‘the electoral system needs reform’—a nice play on words—and there is now a contingent of 72 Liberal Democrat MPs for whom electoral reform is a matter of faith. Notably, now that the electoral system is punishing the Conservatives, who won 18.6% of seats on 23.7% of the vote, we’re even seeing some alarm about disproportionality from the right—the party’s past enthusiasm for First Past the Post notwithstanding.

However, Keir Starmer has—for reasons which are not entirely a mystery—insisted he has no plans to implement electoral reform, so the First Past The Post system appears set to stay. At present, Labour enjoys a set of localised results which do not place its majority in any undue danger. Adding its vote leads together, its effective ‘tipping point’ constituency at which it would lose its majority under a universal swing against the party—Glasgow South West—has a local 9.2 point lead, so only slightly more fragile than the national 10-point lead.

However, if opposition to Labour were to coalesce—say, the Conservatives and Reform UK reached some kind of agreement—or if a particular opposition party were to enjoy a surge, this majority could rapidly melt away. This is especially true in a period of heightened voter volatility; we saw over the last parliament how swiftly a major party can collapse.

The debate over the electoral system will undoubtedly continue in the UK. But proponents of electoral reform are caught in a Catch 22 problem: only smaller parties are incentivised to advocate reform yet the system itself ensures they are rarely in a position to exert influence over government policy. Therefore, until the electoral system happens to produce another hung parliament, or perhaps until the two-party system fully collapses and produces results absurd enough to build cross-party support for change, there is no prospect of electoral reform on the political horizon.