Britain looks set for a future of coalition governments if Andy Burnham succeeds with his push to axe the first-past-the-post voting system for Westminster elections.
The Prime Minister used his Labour conference speech on Tuesday to announce the creation of a new 'national commission' to look at electoral reform.
Mr Burnham, a long-time supporter of proportional representation, demanded a change so that 'everyone's vote counts and everyone's voice is heard'.
Ditching the first-past-the-post system in favour of proportional representation will make it more likely that smaller parties – such as the Greens – form part of a Westminster government.
Mr Burnham's plans have revived warnings that a chaotic 'rainbow coalition' – made up of a variety of Left-wing or nationalist parties – could soon take charge of Britain.
An analysis of general election results since the end of the Second World War shows how Britain would likely have been left without a majority government for more than half-a-century had a proportional representation system been used in past contests.
Research by Electoral Reform Society has estimated the likely results of past general elections using the Single Transferable Vote (STV) system.
This is a form of proportional representation that is already used for elections to the Northern Ireland Assembly.
Britain looks set for a future of coalition governments if Andy Burnham succeeds with his push to axe the first-past-the-post voting system for Westminster elections
The research shows, at the 2024 general election, how Labour would have been left 99 seats short of a majority in the House of Commons if STV had been used.
It means Mr Burnham could now be governing as a minority Labour administration propped up by the Liberal Democrats and the Greens.
In 2019, Boris Johnson would have fallen 18 seats short of a Tory majority at that year's general election under an STV system.
This would have severely imperilled Mr Johnson's chances of fulfilling his pre-election promise to 'Get Brexit Done'.
In 2017, if Theresa May's snap election had been held under an STV system, both the Tories and Labour would have ended up with fewer than 300 seats.
But the parliamentary arithmetic would have made it more likely that Jeremy Corbyn would have been PM - in a minority Labour administration or coalition supported by smaller Left-wing parties - than Mrs May retaining power.
Tony Blair would also have fallen narrowly short of a Labour majority at the 1997 general election if voters had elected MPs using STV, the research shows.
In fact, if STV had been used at all general elections since the end of the Second World War, the study suggests it is likely the last majority government to have been elected in the UK would have been in 1966 under Labour's Harold Wilson.
Under STV, instead of choosing one person to represent a small constituency or ward, voters choose a few people for a larger area.
The idea is that it allows voters to have someone elected who shares their views. On the ballot paper, voters put candidates in order with a 1 beside their favourite candidate, 2 beside their next choice, and so on.
Voters do not have to number every candidate, while parties will stand more than one candidate in each area.
To get elected, a candidate needs to win a set amount of votes, based on the number of vacancies and the number of votes cast.
After the votes have been counted, any candidate who has reached this number of votes is elected.
If they won more votes than they need, these extra votes move to each voter’s second favourite candidate.
Despite the research showing STV would have vastly reduced the number of post-War majority governments in Britain, Mr Burnham in his Labour conference speech on Tuesday suggested it was the current first-past-the-post system that was to blame for recent political turbulence.
He argued that Britain should not be governed by a 'divisive' administration elected with '30 per cent of the vote or less'.
Just ten weeks on from his brutal ousting of Sir Keir Starmer as PM, Mr Burnham told Labour members there was a need to change the country's politics.
He said: 'Westminster prizes point-scoring over problem-solving. And that is why so many things go unfixed for so long.
'If we want to change Britain, we need to change ourselves. I will work as hard as I can to get as much cross-party support for our plan for Britain as I can.
'If we can secure that, it will project a message of confidence and stability to the markets and the world about Britain's future direction.'
The PM has so far refused to call a snap General Election in order to win his own mandate from the country.
This is despite him having called for the Tories to do exactly that when they changed leaders while in power.
But he used his first Labour conference speech as PM to demand a 'new politics', as he bowed to calls from his party's MPs for a national commission on electoral reform.
Mr Burnham added: 'We can't succeed in the eyes of the world if we continue with the levels of political turbulence we have seen in recent times.
'It is always in my mind that I'm the seventh PM in ten years. It is why I want to underpin our plan for Britain with a new politics.
'We will all have failed in our public duties if we carry on as we are and open the door of No10 to a divisive government on 30 per cent of the vote or less.
'Conference, in past years you have voted twice to support electoral reform.
'I hear you, I agree with you and today I am announcing a new national commission on electoral reform.
'I invite all political parties to be a part of its work.
'We will contest the next election with a manifesto commitment to change the electoral system so everyone's vote counts and everyone's voice is heard.'
Labour's party conference voted to support moving towards a proportional representation voting system in 2022.
But the party's 2024 manifesto instead focused its electoral and constitutional changes on extending voting to 16 and 17-year-olds and House of Lords reform.