Keir Starmer is under mounting pressure from Labour activists to make reform of the voting system a manifesto commitment, amid rising public concern about its unfairness and fears that it could leave left-of-centre parties out of government for good.

With Labour and Starmer searching for a “big idea” to reignite his leadership, polling today for the Best for Britain organisation shows that less than two fifths of people (39%) believe their vote has made any difference to the results in recent first-past-the-post elections.

The same poll of more than 3,000 adults found 52% of voters supported some form of electoral reform to make the number of elected representatives better reflect the total of votes cast, while only 17% opposed it.

Some 64% of Labour supporters were in favour, and even 50% of Conservatives liked the idea. Support climbed to 52% in Leave-voting Conservative seats, where just 15% opposed it. In many cases these are the very seats that Labour needs to win if it wants to oust the Tories from power.

At the same time local Labour parties – desperate to break the right’s grip on Downing Street - are increasingly throwing their weight behind a motion backing a switch to some form proportional representation. Currently 216 Constituency Labour Parties (CLPs) have supported the motion, placing Starmer and the party high command under intense pressure to act at this autumn’s party conference.

In the run up to the 6 May local elections, research for the Politics for the Many campaign showed that the “winner-takes-all” voting system meant voters on the left were “in effect being punished for having a choice of parties to vote for”. The research showed that in nearly half of wards (48%), there was one unified party on the right (the Conservatives) standing candidates against three candidates from parties on the progressive “left”: Labour, the Liberal Democrats and the Greens. In 85% of wards, there were more “left” parties standing candidates than “right” parties.

Nationally the Conservative Party now holds a working majority of 87 seats in the House of Commons having won 42% of the vote at the last general election in December 2019. The Conservatives gained 48 seats having only increased their vote share by 1.2%. As a result of the First Past the Post system the Tories required 38,000 votes to elect each of their MPs, compared with 51,000 for every Labour seat, 300,000 for each Liberal Democrat and 900,000 for the single Green MP.

Naomi Smith, Chief Executive of Best for Britain said: “Our polling shows most people feel their vote just doesn’t matter, they want a fairer electoral system and they want like-minded parties to work together to deliver it.

“Labour has a choice. It can languish in opposition most of the time under the current system, or be the biggest party in power most of the time.”

During his campaign for the leadership Starmer came out in favour of change saying: “We’ve got to address the fact that millions of people vote in safe seats and they feel their vote doesn’t count. That’s got to be addressed. We will never get full participation in our electoral system until we do that at every level.”

But with the Tories certain to oppose any change to a system that benefits them, Labour knows it will have to be returned to power under the current arrangements before it can implement reform.

After four general election losses and the recent local election setbacks there are now growing calls for Labour to abandon its caution, and join so-called “progressive alliances” with the Liberal Democrats and Greens. Under such alliances the parties with the least support would stand aside or not campaign actively at future elections, to ensure the left of the centre votes was maximised behind a single candidate.

Already calls are growing within the Labour, Liberal Democrat and Green Parties to co-operate ahead of upcoming by-elections in Batley and Spen, where Labour selects its candidate on Sunday, and Amersham over the coming months.

Neal Lawson – director of the Compass think tank which has been pushing the idea of Progressive Alliances since 2017 said: “Before our eyes the centre-left field of politics is being reshaped. As the right bloc consolidates and strengthens post-Brexit, the centre left, is being forced into a new politics of alliances.

“This realignment is taking place first in councils across the country as progressives are choosing to work together to keep the Tories out.

He added: “Normally talk of a progressive alliance happens two months before an election. Now it’s happening two years out because everyone knows Labour cannot and will not win on its own. There is the time and the demand to build a new politics for a new society – time for Labour to win with others or lose alone once more.”

Joe Sousek, an organiser for Labour for a New Democracy and co-founder of the Make Votes Matter organisation, said: “Proportional Representation now has overwhelming support among the Labour membership. Three quarters of Labour members support PR, a third of all local branches have carried motions in favour, and just this week another affiliated trade union - ASLEF - came out in support of electoral reform. The Labour Party needs to embrace these clear demands and commit to a fair, proportional voting system in which our Parliament reflects the people it governs.”