Politics Home Article | How Will A Labour Leadership Contest Work?

Keir Starmer’s rivals are preparing to launch a contest for the Labour leadership (Alamy)

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Starmer’s rivals are lining up to launch a leadership contest. Streeting has published his letter to Starmer announcing his resignation from the Cabinet, writing that he had “lost confidence in your leadership” and that it would be “dishonourable and unprincipled” to stay in post.

Former deputy Labour leader Angela Rayner has said she had settled her unpaid council tax bill of £40,000, and her allies have briefed that she would be prepared to stand in any leadership contest if needed.

Labour Greater Manchester mayor Andy Burnham – who served as a minister during the Blair and Brown governments – also wants to run as leader, but is currently sitting as a Labour MP and therefore unable to enter the race.

Labour’s ‘soft left’, including senior members of the influential Tribune group of MPs, will push the party’s ruling body to allow for Burnham’s inclusion in a leadership race if one is triggered imminently. But huge questions remain over whether Burnham will be able to find a seat to run in and win a by-election before nominations for a leadership race take place.

So far, Starmer has insisted he will not stand down, saying in a speech on Monday that he will not step down as PM, as he did not want to “plunge the country into chaos”. In an appeal to his own MPs, he said that the governments constantly changing their leadership was “damaging”.

Should Starmer refuse to leave, he is automatically entitled to be on the ballot paper as the sitting Labour leader and current prime minister.

As a leadership challenge looks imminent, how will a contest work, and how long would it take?

The process for a Labour leadership election

There are two main paths to replacing a Labour prime minister, with the process differing significantly from that of the Conservative Party, which held multiple leadership elections during its time in power between 2010 and 2024. 

A leadership contest can be triggered by either Starmer resigning or by another Labour MP gaining the support of 80 MPs – or 20 per cent of sitting Labour MPs – to challenge him for the leadership. Before 2021, an MP only needed the support of 10 per cent of the Parliamentary Labour Party to stand. 

The candidates then need to win nominations from the Constituency Labour Parties and affiliates. The final stage is an alternative vote – also known as a preferential ballot – where party members and affiliates rank their preferred candidates. Voters only have one vote. Votes are then redistributed by ranking until one candidate receives over 50 per cent of the vote; the candidate that reaches the threshold first wins the leadership contest and becomes Labour leader and prime minister of the United Kingdom.

Labour leadership contests can drag on for months. In practice, a full Labour leadership contest usually takes more than 12 weeks.

The formal process under Labour’s current rules is as follows:

1. The leader resigns or is challenged
2. Labour’s National Executive Committee (NEC) sets the timetable
3. Candidates need nominations from MPs (candidates need to reach the threshold of 81 nominations, 20 per cent of the current Parliamentary Labour Party)
4. Candidates then need to win nominations from the Constituency Labour Parties and affiliates
5. The third stage is the members and affiliates vote
6. The result is announced

The NEC has significant flexibility over the nomination thresholds, the timing of voting ballots, the schedules for hustings and the overall pace of the contest.

How long did previous Labour leadership contests take?

• 2020 Labour Party leadership election (Keir Starmer succeeds Jeremy Corbyn) About 16 weeks from resignation announcement to result or about 13 weeks from formal opening to result
• 2016 Labour Party leadership election (Corbyn challenged by Owen Smith) About 13 weeks from revolt to result
• 2015 Labour Party leadership election (Corbyn elected leader) About 18 weeks. One of Labour’s longest modern contests.
• 2010 Labour Party leadership election (Ed Miliband beats David Miliband) About 19 weeks. Again, very long because it followed a general election defeat and involved a full summer campaign.

The process for a parliamentary by-election

If Burnham is to run in the contest, he would have to be serving as an MP before the initial nominations for a leadership – which currently looks very difficult for the Manchester mayor to achieve.

Polling day for a parliamentary by-election is usually held about 4 to 8 weeks after an MP announces their intention to stand down.

If an MP stands down for Burnham, the process for a parliamentary by-election would be as follows:

1. The seat would become vacant
2. Labour whips would need to move the writ
3. Burnham would need NEC approval as a candidate
4. And then win the by-election

Labour whips usually control when the writ is moved, and the party could theoretically slow-walk the process, delay the by-election, or complicate Burnham’s route back.

How long did previous Labour leadership contests take?

• Gorton and Denton by-election, 2026 – just under 5 weeks
• Runcorn and Helsby by-election 2025 – about 6½ weeks
• Rutherglen and Hamilton West by-election 2023 – around 9 weeks
• Mid Bedfordshire by-election 2023 – around 7 weeks
• Uxbridge and South Ruislip by-election 2023 – around 6 weeks
• Tamworth by-election 2023 – around 6 weeks
• Selby and Ainsty by-election 2023 – around 4.5 weeks
• Hartlepool by-election 2021 – around 7 weeks