New analysis produced exclusively for the Guardian reveals how different voting systems would return significantly different seat totals in the UK parliament, based on recent polling. While the current first past the post (FPTP) system could leave Labour short of a majority with 250 seats, the modelling shows how proportional systems would be likely to reduce the number of seats given to the leading party – and give the UK a more finely balanced parliament that better represents the votes people cast.
Burnham's electoral reform push
The prime minister, Andy Burnham, has announced a new national commission on electoral reform aimed at changing the electoral system, a plan supported by more than 100 Labour MPs as well as parties such as the Liberal Democrats, the Greens, the SNP and Plaid Cymru. Electoral reform has enjoyed increased public support in recent years.
The research conducted by More in Common suggests that, under proportional systems such as single transferable vote or regional party list, the UK could end up being governed by a minority government – or a progressive alliance of parties.
How proportional systems could change the map
Proportional representation (PR) aims to produce a parliament that more closely reflects how people voted, allowing voters to back their preferred party without worrying about tactical voting. It often makes it harder for a single party to win a majority and is more likely to result in coalition governments.
Alongside the current first past the post system, More in Common modelled three different PR systems for the Guardian: regional party list, single transferable vote (STV) and additional member system (AMS).
The More in Common research shows that no single party would achieve a majority according to their projected polling, regardless of which system is used. The current FPTP system would come the closest, giving Labour 39% of the seats off just 26% of the vote – still short of a majority. The party would most likely need the support of the Lib Dems and the SNP to form a majority government.
The proportional systems would not give Labour such a boost: regional party list is estimated to give the party 26% of seats off 26% of the vote; AMS would give it 26% of the seats off 29% of the vote; and STV would give it 27% of the seats off 28% of the vote.
Smaller parties gain under PR
Under each of these systems, either a progressive coalition of parties – a combination of Labour, the Lib Dems, the Greens, the SNP or Plaid Cymru – or a Reform-Conservative-Restore coalition would be the only paths to forming a government. Even then, several scenarios would lead to a minority government in a finely balanced parliament.
While the leading Labour party would lose the largest proportion of seats under the proportional systems, smaller parties would be the biggest winners. The Green party would win only three seats under FPTP under current polling, but more than 50 seats in all three PR systems that we're modelling – 9% of the seats on offer, more closely matching their vote share. Likewise, the far-right Restore Britain party would surge above 30 seats in each of the PR systems, compared with winning just one seat under FPTP.
Charlie Buckley, a senior research associate at More in Common, said: “With [Nigel] Farage’s [Reform UK] party having lost some momentum and Andy Burnham being – for now – a more popular prime minister, it’s Labour who would reap the benefits from our current electoral system. Despite only being four points ahead of the Tories, our model shows Labour winning double the number of seats under first past the post, while a proportional system would give us a parliament which better reflects the close three-horse race we now have between Labour, Reform and the Conservatives.”
Burnham said in his conference speech that Labour shouldn't “open the door” to a “divisive government” that could win power on “less than 30% of the vote”.
Regional impact and local representation
The proportional systems were more likely to remove the regional dominance of any one party. In London, Labour is estimated to gain 69% of seats under FPTP. This number would drop dramatically under PR, to 37% in the party list system and 42% under AMS. Reform and the Greens would be the biggest beneficiaries in the capital: while Reform would win one seat and the Greens nothing under FPTP, they'd collectively win 18 seats – nearly a quarter of London's seats on offer – under the party list system.
The same disparity can be seen in the east of England, with the poll-leaders there, Reform, gaining 43% of the seats under FPTP but falling to 29% under both the party list and AMS systems.
Use the postcode search below to see how your local representation would change under each system. Under systems that use regional vote counts to produce more proportional results, you would have regional representatives in place of – or in addition to – constituency ones.
What is wrong with first past the post?
The most recent polling in Britain, as well as recent elections, show an unprecedented fragmentation of the political system. Labour leads on an average of 26%, with Reform second on 23% and the Conservatives third on 20%. The Greens and the Lib Dems are each polling at 10%. This is based on an average of the last 10 polls, with Labour enjoying a slim lead in the national polls since the party chose Burnham as its new leader and prime minister.
With three parties clustered closely together in the polls, the FPTP system means small shifts in vote share could produce highly volatile and sometimes counterintuitive seat projections, as marginal changes in local contests are amplified into large swings in parliamentary representation.
In the last general election, Labour won 411 of 650 seats with just 34% of the vote. A report from the Electoral Reform Society modelled the 2024 vote under different voting systems. Only first past the post gave Labour a majority, with all proportional systems giving smaller parties more representation and leading to a hung parliament.
There have been renewed calls for proportional representation. In his conference speech, Burnham said: “We will contest the next election with a manifesto commitment to change the electoral system so that everyone's vote counts and everyone's voice is heard.” Farage has also previously called for electoral reform, calling the current system “outdated” and “not fit for purpose”, but has gone quiet on the subject since Reform went on to lead the polls – until Burnham's Labour retook a slim lead.
Could the voting system change?
Experts say any attempt to introduce proportional representation for Westminster elections would be likely to face strong pressure for a referendum, given its significance as a constitutional change and the precedent set by the 2011 referendum on the alternative vote system (AV). The referendum saw voters decisively reject AV, showing the difficulty of winning public support for electoral reform. Experts warn that any future move to proportional representation could face similar challenges, as voters are familiar with first past the post and may be reluctant to replace a system they already understand.
Buckley said: “The real winners with a PR system would be on the edges of the political spectrum. The Greens would go from a handful of MPs to a sizeable bloc, while Restore Britain would arrive in parliament in numbers, potentially giving these smaller parties a kingmaker role in the formation of coalitions. So the prospect of forming a workable majority – already a dubious one in our current electoral system – looks even more complicated under a proportional one. Regardless of the system in place, our fragmented politics would make any election in Britain a challenge for those seeking to enter and control government, and the idea of a 'commanding majority' is out of reach for all the major parties right now.”
When More in Common conducted similar modelling in July, Reform was leading in the polls, and they found the proportional systems would equally not give Reform the same seats boost that FPTP would. The researchers said then that it was difficult to predict how voters might adjust their own behaviour under a new system.
Darren Hughes, the chief executive of the Electoral Reform Society, told the Guardian: “The prime minister's pledge for a new commission to look at electoral reform is an important step in the right direction. This needs to be an independent and trusted process that focuses on making sure parliament properly reflects the way the country voted. There is a growing problem with our democracy in that parliament is looking less and less like the way people voted. The last general election saw the biggest mismatch in British history between the votes people cast and the seats parties won. This is largely due to the fact that our outdated two-party voting system can't cope with the multiparty politics we now have, and is throwing up increasingly distorted and unstable results. Simply put, bringing in a system of proportional representation would mean parliament better reflects how the country voted by making sure seats match votes.”
Latest polling and seat distribution figures were provided by More In Common (MIC). Alternative electoral system modelling is based on MIC and Guardian assumptions about constituency boundaries. Party list uses 11 regions – the nine official English regions plus Scotland and Wales – with variable seat totals. AMS uses a combination of the eleven regions and 631 existing first past the post constituencies. STV uses 52 subregional constituencies – composed of the current FPTP constituencies – of variable size depending on aggregate population. Northern Ireland and the Commons speaker's seat of Chorley are excluded from the modelling. This results in 631 total modelled seats for FPTP, STV and party list systems, and in 1,052 seats for AMS. The exact details, shown as seat totals, boundaries and regional groupings, are based on assumptions on how the new proportional systems could work, and in reality, these totals and exact workings would vary should another voting system be adopted.
