Labour backbenchers are pushing to cap political donations from wealthy UK-based donors, a move campaigners believe could win the support of dozens of MPs and Andy Burnham, the frontrunner to become the next prime minister.

The proposal, which would extend donation limits beyond the narrow overseas-donor rule the government has already enacted, has gained fresh momentum after Burnham confirmed he backs a domestic cap – putting him at odds with the position held by Sir Keir Starmer's outgoing government. In correspondence with a campaigner, Burnham said he wanted to see a limit introduced to stem the tide of big money in politics.

With Burnham now the clear favourite in the Labour leadership contest, supporters believe a domestic cap could become party policy in the coming months, reopening a debate ministers have so far resisted.

The campaign centres on an amendment to the Representation of the People Bill tabled by Alex Sobel, the Labour MP for Leeds Central and Headingley and chair of the All-Party Parliamentary Group for Fair Elections. His amendment would limit donations from UK donors to £1 million a year, building on the government's newly introduced £100,000 annual cap for British citizens living abroad.

Backers argue that the principle of preventing wealthy individuals from buying influence in politics should apply to domestic donors as well as those overseas. Sobel's team suggest the relatively high £1 million threshold may prove difficult for the government to object to, even though ministers have previously rejected caps for donors based in the UK.

The UK remains an international outlier on the issue. Unlike parliamentary democracies such as Canada and Australia, it does not limit how much any individual or organisation can give to a political party or its members, despite all the largest parties in Parliament backing the introduction of some form of limit over the past 20 years.

The reliance on major donors has grown sharply. In 2015, only 1% of private donations came from companies and individuals giving £1 million or more; by 2024, that figure had risen to more than a third, at 35%. Election spending has climbed too, with parties and candidates spending more than £90 million at the 2024 general election – nearly an 80% increase on the £51.7 million spent in 2015.

The immediate trigger for the renewed push has been Reform UK's funding. Christopher Harborne, a Thailand-based crypto billionaire, donated £9 million to the party in December 2025, the largest ever donation by a living individual, and has given around £12 million over the past year – roughly two-thirds of Reform's recent funding.

That donation prompted the government to commission the Rycroft Review into foreign financial interference, led by former Permanent Secretary Philip Rycroft. Published on 25 March 2026, the review made 17 recommendations. Ministers acted immediately on two of them, introducing a £100,000 annual cap on donations and regulated transactions such as loans from British citizens living abroad, alongside a ban on all cryptocurrency donations. Both measures came into force this week.

Once the legislation is in force, political parties and regulated entities such as candidates and MPs will have 30 days to return any unlawful donations received in the interim, after which enforcement action can be taken.

Campaigners said the overseas cap was significant in principle, marking the first time a British government had accepted the idea of limits on political donations. But they argue the government has left a major gap by refusing to extend the cap to domestic donors.

Burnham has gone further than Sobel's proposal, saying he would like to see a UK donation cap reduced over time and calling for a "wholesale culture change" at Westminster. The proposal was set out in correspondence with Shaun Bowler, founder of the grassroots democracy campaign WakeUpGB.

"Big money always comes with big demands that skews democracy away from the many to the very few – Burnham is right to end it," said Neal Lawson, director of the Compass think tank and a Burnham ally.

Burnham also supports a linked amendment tabled by Sobel to create a National Commission on Electoral Reform, the most signed of the backbench proposals, with more than 100 MPs – most of them Labour backbenchers – now backing it. Burnham has indicated he would commit to electoral reform in Labour's next manifesto, potentially giving him a mechanism for moving towards proportional representation should he become leader.

Sobel's cap is one of several backbench amendments in the same package. Others include a proposed ban on donations from property developers, tabled by Chris Hinchliff, and an amendment from Neil Duncan-Jordan that would bar donations from any individual or firm awarded a public contract within the previous ten years, in an effort to clamp down on corruption. Emily Darlington has tabled a series of amendments on digital and artificial intelligence.

The leadership backdrop has sharpened the significance of the campaign. Starmer announced his resignation on 22 June 2026, after Burnham won the Makerfield by-election and Labour MPs called for an immediate leadership challenge. Nominations for the contest open on 9 July and close on 16 July. Burnham has confirmed he will stand, while Health Secretary Wes Streeting has said he will not contest the leadership.

The wider cap nonetheless faces steep procedural odds. At the bill's committee stage, held over nine sittings between 18 March and 16 April, several opposition and backbench amendments were proposed but none was agreed; only government amendments passed. The 2024-26 session of Parliament ended on 29 April without the bill progressing further.

There is also a substantial gap over the level of any cap. The Committee on Standards in Public Life has recommended a far tighter limit of £10,000 a year on donations from any individual or organisation, well below Sobel's proposed £1 million threshold. Campaigners have acknowledged that a £1 million cap "may have a limited impact on public confidence", suggesting some MPs will want to go further.

A separate flashpoint concerns corporate donations. The government's bill caps company donations at UK revenue, but the Electoral Commission has warned the measure is toothless as drafted, because the limit applies separately to each recipient. This means a company could donate an amount equal to its revenue to a party and then donate the same again to each of the party's MPs, councillors and candidates.

"Under the current proposals, company donations would effectively remain uncapped," the Commission said, recommending that a company's profit, rather than its revenue, be used as the measure of its UK earnings. The concern was echoed by the Rycroft Review and the Joint Committee on the National Security Strategy, which recommended that limits on corporate donations apply per company rather than per recipient.

Electoral Commission figures underline the scale of party funding. It reported £24.7 million in donations to UK political parties in the first quarter of 2026 alone. Corporate donations have risen from £13.6 million in 2017 to £30.6 million in 2024, and companies donated £242 million to political parties between 2001 and the end of 2025, making up 16.9% of all donations in that period.

Any domestic cap could also carry risks for Labour itself, given the party's reliance on trade union funding, while two of Reform's donors have already said they will challenge the overseas cap in the courts. A domestic limit would face a legal challenge that in a similar case in Victoria, Australia, resulted in the voiding of all the state's political finance regulations shortly before an election.