More than 60 MPs are calling for a rethink of the UK's first-past-the-post voting system, which they have labelled "broken".
They are backing a new national commission to examine the current system for elections to the House of Commons and recommend reforms.
Critics have long said the first-past-the-post system means candidates can be elected on a relatively low share of the vote, undermining democracy, but defenders say it means decisive results and, in theory, more stable government.
The new political backdrop of multi-party politics which has emerged in recent years, with smaller parties challenging Labour and the Conservatives, has reignited calls for electoral reform.
First past the post is the voting system for UK general elections and elections to English councils.
This means the candidate with the most votes wins in a constituency and becomes an MP, while the party with the most MPs wins the election.
Reform UK, the Lib Dems, the Green Party, SNP and Plaid Cymru have all argued for a more proportional voting system.
This would link a party's share of seats in Westminster more closely to the share of votes they receive overall.
The Conservatives want to stick with first past the post.
Prime Minister Sir Keir Starmer supported electoral reform during his bid to become Labour leader in 2020 but has since dropped his pledge and did not include it in the party's 2024 general election manifesto.
Some 64 Labour MPs have now signed up to an amendment to the Representation of the People Bill, calling for a national commission on electoral reform.
The amendment has been tabled by Alex Sobel, the Labour MP for Leeds Central and Headingley.
Sobel, who is also chairman of the All Party Parliamentary Group (APPG) for Fair Elections, urged MPs from all parties to join the "common sense" call ahead of the bill's expected return to the Commons next month.
"The prime minister in his reset speech said 'a return to the status quo would not be enough for people'," he said.
"First past the post is one of the biggest examples of a broken status quo in UK politics.
"A very modest part of any reset would be to accept and announce a National Commission for Electoral Reform."
In 2022, Labour members at the party's annual conference voted in favour of a commitment to introduce proportional representation for general elections.
Eight out of Labour's eleven affiliated trade unions also have formal policy in favour of electoral reform.
The issue was last examined by the Jenkins Commission in 1998, which recommended first past the post should be replaced by a new proportional system for UK general elections. However, this was not implemented.
In a 2011 referendum, the UK voted overwhelmingly against replacing first past the post for general elections with a method known as the alternative vote (AV) system, which asks voters to rank candidates in order of preference.
