Prime Minister Andy Burnham is facing pressure from almost 100 Labour MPs to accelerate electoral reform, with 98 of his own MPs backing a parliamentary push for a National Commission on Electoral Reform.
The Labour MPs are among 185 MPs from across eight parties and independents reported to be supporting an amendment to the Representation of the People Bill, which returns to the Commons for its remaining stages on 2 September.
The move creates an early test for Burnham, who has previously backed proportional representation but whose Government has not committed to changing the voting system during the current Parliament.
98 Labour MPs back electoral reform push
The amendment has been tabled by Labour MP Alex Sobel and would require the Secretary of State to publish a report within three months of the legislation passing on the feasibility of establishing an independent National Commission on Electoral Reform.
The proposed commission would review the voting system used for elections to the House of Commons and make recommendations intended to ensure that it is fair, representative and capable of sustaining public confidence.
Parliament's website records that the amendment has not yet been considered by the House of Commons and no decision has been taken.
Amendment would not itself introduce proportional representation
The amendment would not itself abolish First Past the Post or replace it with proportional representation.
Instead, it would require ministers to report on the feasibility of creating a commission. Under the proposed terms, any commission would be independent of Government, involve expert and public participation and publish its recommendations within 12 months of being launched.
That distinction is important because MPs backing the proposal are seeking to begin a formal process of examining electoral reform rather than directly changing the voting system through the current Bill.
Burnham faces pressure over previous support for reform
The push is politically significant because Burnham has been a longstanding supporter of electoral reform.
At Labour conference last year, before becoming Prime Minister, he backed the call for a national commission and supported a future manifesto commitment to introduce a proportional system for Westminster elections.
Downing Street has said Burnham remains strongly committed to electoral reform but regards changing the voting system as a matter for a future Labour manifesto because a mandate would need to be secured.
That leaves the Prime Minister facing pressure from MPs who want the Government to begin the review process now, even if any eventual change to the voting system takes place only after another general election.
Government previously rejected national commission
In a written parliamentary answer published in March, the Government said it had no plans to establish a National Commission on Electoral Reform.
Ministers instead pointed to measures in the Representation of the People Bill designed to increase democratic participation, including votes at 16 and changes to voter registration.
The new amendment therefore provides MPs with a parliamentary mechanism to press the Government to reconsider that position.
Bill returns to Commons on 2 September
The Representation of the People Bill is due to return to the House of Commons for its remaining stages on Wednesday 2 September.
The wider legislation includes measures to lower the voting age to 16, introduce more automated electoral registration, expand accepted forms of voter identification and strengthen rules around political donations.
It remains unclear whether the electoral reform amendment will ultimately be selected or put to a vote, and some MPs who have subsequently joined the Government frontbench may withdraw their support in line with parliamentary convention.
However, the number of Labour MPs backing the proposal demonstrates the scale of pressure on Burnham to turn his longstanding support for electoral reform into a formal Government-led process.
First Past the Post debate returns
Westminster elections currently use First Past the Post, under which the candidate receiving the largest number of votes in each constituency is elected.
Supporters of proportional representation argue that a replacement system would make the composition of Parliament more closely reflect votes cast across the country.
Opponents have traditionally argued that First Past the Post provides clear constituency representation and can make it easier to produce stable majority governments.
The proposed commission would be intended to examine those competing arguments and recommend whether the system should be reformed.