A study by the Electoral Reform Society (ERS), which campaigns for a new voting system to be introduced in the UK, found the current first-past-the-post (FPTP) system favoured the Conservatives and deprived Labour of up to 35 House of Commons seats.
Use of a different system could have seen the Liberal Democrats win more than three times as many seats as the 12 they secured under FPTP – enabling Jeremy Corbyn to join forces with them and enter Downing Street as the leader of a left-wing coalition with a parliamentary majority.
Under FPTP, however, the majority of votes have little impact. The ERS said 22 million votes – around two-thirds of the total – were “wasted” because they were cast for candidates who did not win or for the winning candidate above the threshold they needed to secure the seat.
In five constituencies, (Manchester Gorton, Liverpool Walton, Knowsley, Liverpool Riverside, Liverpool West Derby) more than 90 per cent of votes cast had no impact on the overall election result.
The research found that, in an attempt to ensure their vote mattered, 6.5 million people voted tactically in the 2017 election because the party they most supported was unlikely to win in their constituency.
FPTP means a very small number of voters in marginal constituencies ultimately determine the entire election result. The study found that if just 0.0016 per cent of the electorate had voted differently, the Conservatives could have won an overall majority – sparing Theresa May the embarrassment of having to make a deal with the Democratic Unionist Party (DUP).
Other voting systems would have delivered a different result.
The ERS and YouGov asked 13,000 people how they would have voted under a range of different systems.
The Single Transferable Vote (STV) system, which is used in Northern Ireland and for local elections in Scotland, would have resulted in Labour winning the most seats – 297 to the Conservative’s 282. The Liberal Democrats would have gained 29 seats instead of 12, while the SNP would have seen theirs cut from 35 to 18.
The Alternative Vote (AV) system and Additional Member System (AMS) would also have seen the Tories’ number of seats cut significantly, with Labour and the Liberal Democrats the main beneficiaries. Under AV, Labour would have gained another 24 seats, mostly at the expense of the Conservatives.
AMS, which is currently used for elections to the devolved assemblies in Scotland, Wales and London, favours smaller parties more than any other system. It would have given Ukip 11 parliamentary seats and the Green Party seven. The Liberal Democrats would have secured 39 – more than three times their total under FPTP. Labour and the Conservatives would both have won fewer seats.
The Conservatives currently benefit most from the status quo and the party would lose seats under any other voting system.
FPTP also entrenches divisions between regions: in the South East, for example, Labour won 29 per cent of the vote but just 10 per cent of seats, while the Conservatives won 34 per cent of ballots cast in the North East and just 9 per cent of seats.
Darren Hughes, Chief Executive of the Electoral Reform Society, said: “For the third time in a row, Westminster’s voting system has failed to do what it says on the tin – produce a strong and stable government.
“June’s election has shown first-past-the-post is unable to cope with people’s changing voting habits – forcing citizens and parties to try and game the system. With an estimated 6.5 million people holding their nose at the ballot box, voters have been denied real choice and representation.
“This surge in tactical voting – double the rate of 2015 – meant voters shifted their party allegiances at unprecedented rates, with the second highest level of voter volatility since the inter-war years.
“A system designed for two parties cannot accommodate these complex electoral swings. In the nations and regions of the UK, elections now feel more like lottery than a real choice.
“As we’ve shown, tiny shifts in the vote result in drastically different outcomes. Having results hinge on a few hundred voters is no way to run a modern democracy.mThe vast majority of votes are going to waste, with millions still stuck in the electoral black hole of winner-takes-all.”