The aim of the British electoral system is not to represent the British people in Parliament but to choose a party to govern that voters can hold accountable when it seeks re-election. Accountability is more easily enforced when a single party governs than it is when there is a coalition government with ministries distributed among three or four parties. The system strengthens accountability by manufacturing a parliamentary majority for a party with a minority of the popular vote. In 2024 disproportionality reached a record height. Labour won more than three-fifths of MPs with only one-third of the national vote.
In all but three elections since 1945 the electoral system has manufactured a parliamentary majority to maintain a Labour or Conservative government. However, since last November it has been failing to do so by an increasingly large margin. It is now odds on that no party will have a majority in the House of Commons. Electoral Calculus predicts that the most likely outcome, Reform winning the most seats, would leave it 81 short of a parliamentary majority. There is only an 11 percent probability of Reform winning an absolute majority.
The current three-way division of the vote is making the first-past-the-post system more proportional. This poses the biggest threat to Labour. Instead of benefiting from the first-past-the-post system, on current form Labour would gain just over a quarter of MPs with just under a quarter of the national vote. A reduction in disproportionality would also keep the Conservatives from winning a parliamentary majority by gaining 38 percent of the popular vote as David Cameron did in 2015.
Reform is the big winner of the move toward more proportional representation. At the last election it won less than one percent of MPs with more than 14 percent of the vote. The current division of public opinion shows it would be over-represented in the next House of Commons. With 25 percent of the vote it could win 37 percent of MPs. This would not be enough to give Reform control of Parliament. In theory, a stable government with 339 seats, an absolute majority, could be formed with Nigel Farage in Downing Street and the Conservatives as a junior partner.
A Labour-led government supported by the Liberal Democrats and SNP would still be 46 seats short of a parliamentary majority. In theory, the Labour, Conservative and Lib Dem parties could form a three-way coalition to keep Nigel Farage out of Downing Street, as the chief opposing parties in Germany have done to keep an extreme right-wing party out of office. But that would only be possible if the situation were desperate as well as serious.
If weeks of bargaining did not form a government that could win a parliamentary vote of confidence with the help of abstentions, a second election would need to be held. if the electoral system once again failed to produce a government, this could lead to the death of the first-past-the-post system.
Prof Richard Rose, Britain's senior psephologist, is currently writing a book entitled The British Party System Under Stress: a Guide to the 2029 Election.