How different levels of donation caps could affect political parties: sensitivity analysis
Summary
This report sets out the potential impact of imposing different caps on donations to political parties. We look at the impact that limits of £100k, £50k and £10k could have had on political parties if they had been in place between the years 2020 to 2025.
Key findings
- Donations caps would have had the largest impact in 2023 and 2024, as donations increased in the lead up to the 2024 General Election
- The Conservative and Labour parties would have seen the greatest net reduction in the amount they received in donations
- Reform’s donation profile changed significantly between 2020 and 2025. In 2025, donation caps would have caused the largest net reduction for them out of all the parties
- In general, the caps would have least affected parties that receive a large amount of smaller donations. Political parties that received standalone large donations would have been most impacted by the cap limits
We estimated the effect of imposing donation caps by identifying all reported donations that exceed each cap level and subtracting the excess amount. For example, if a donor gives £10,500 under a £10k cap model, the £500 above the cap is removed from the amount received by the party. The calculation is carried out separately for each party and each year, covering the nine parties receiving the highest total donations.
Data includes reportable donations from individuals, companies, trade unions, trusts and unincorporated associations The analysis assumes that all other aspects of electoral law remain the same. For example, donations from trade unions are treated as subject to the different caps in the same way as individuals and other organisations.
The figures are estimates of the impact that different levels of cap could have on political donations in the UK. They are not definitive figures. This is partly due to data quality issues, such as where parties submitted donations from the same donor inconsistently (e.g. under different titles or spellings).
Additionally, the model can’t account for how caps would change behaviour. For example, donors who donated to multiple parties may have chosen to only donate to one if there had been a cap.
The model only accounts for reported donations in each year. Before 2024, the threshold for reporting donations was £7,500; from 1 January 2024, the threshold increased to £11,180. Any donations under these amounts are not included in this analysis.
It also does not consider funding parties receive from other sources, e.g. membership fees.
The impact of caps by level, year and party
Where percentage changes are shown these represent the change in the volume of reported donations, not total party income.
By level of cap
Logically, a £100k cap would have resulted in the smallest reduction to party donations across the entire five-year period:
- A £100k cap would have resulted in a £181 million (57%) reduction in donations.
- A £50k cap would have resulted in a £211 million (66%) reduction in donations.
- A £10k cap would have resulted in a £273 million (86%) reduction in donations.
By year
Across the individual years, caps would have made particularly large impacts on donations in 2023 and 2024. This is given the higher levels of donations in the run up to the 2024 General Election.
Figure 1: Total amount of donations with caps across the years
| Actual total donations | Estimated donations with £100k cap | Estimated donations with £50k cap | Estimated donations with £10k cap | |
|---|---|---|---|---|
| 2020 | £29m | £15m | £12m | £6m |
| 2021 | £38m | £21m | £17m | £7m |
| 2022 | £38m | £21m | £17m | £7m |
| 2023 | £79m | £25m | £20m | £9m |
| 2024 | £84m | £34m | £26m | £11m |
| 2025 | £50m | £22m | £16m | £6m |
By party
Table 1 shows how different levels of donation cap would have affected the nine political parties who raised the most in donations. We look at the overall total of donations across the five-year period from 2020-2025.
| Party | Total reported donations 2020-2025 |
|---|---|
| Conservative and Unionist Party | £142.2 million |
| Labour Party | £97.6 million |
| Liberal Democrats | £31.3 million |
| Reform UK | £24.2 million |
| Scottish National Party (SNP) | £2.4 million |
| Co-operative Party | £5.4 million |
| Green Party | £2.9 million |
| The Reclaim Party | £4.3 million |
| Sinn Féin | £2.2 million |
| Other | £6.5 million |
| Total | £319 million |
| Party | Estimated total reportable donations if there had been a £100k cap | % decrease in donations |
|---|---|---|
| Conservative and Unionist Party | £64.2 million | 55% |
| Labour Party | £28.1 million | 71% |
| Liberal Democrats | £26.7 million | 15% |
| Reform UK | £6.7 million | 72% |
| Scottish National Party (SNP) | £1.5 million | 40% |
| Co-operative Party | £2.1 million | 61% |
| Green Party | £2.7 million | 7% |
| The Reclaim Party | £600,000 | 86% |
| Sinn Féin | £822,000 | 62% |
| Other | £4.3 million | 34% |
| Total | £137.7 million | 57% |
| Party | Estimated total reportable donations if there had been a £50k cap | % decrease in donations |
|---|---|---|
| Conservative and Unionist Party | £51.6 million | 64% |
| Labour Party | £20.4 million | 79% |
| Liberal Democrats | £22.7 million | 28% |
| Reform UK | £4.4 million | 82% |
| Scottish National Party (SNP) | £999,000 | 59% |
| Co-operative Party | £1.5 million | 72% |
| Green Party | £2.3 million | 20% |
| The Reclaim Party | £300,000 | 93% |
| Sinn Féin | £519,000 | 76% |
| Other | £3.5 million | 47% |
| Total | £108.2 million | 66% |
| Party | Estimated total reportable donations if there had been a £10k cap | % decrease in donations |
|---|---|---|
| Conservative and Unionist Party | £21.1 million | 85% |
| Labour Party | £7.9 million | 92% |
| Liberal Democrats | £11.7 million | 63% |
| Reform UK | £1.3 million | 95% |
| Scottish National Party (SNP) | £327,000 | 87% |
| Co-operative Party | £473,000 | 91% |
| Green Party | £1.4 million | 53% |
| The Reclaim Party | £60,000 | 99% |
| Sinn Féin | £154,000 | 93% |
| Other | £1.5 million | 77% |
| Total | £45.9 million | 86% |
Overall, caps would have had the largest net impact on the Labour and Conservative parties. However, all parties would have experienced more of an impact in election years. There is a detailed breakdown of the impact of caps per party per year in Figure A in the Appendix which illustrates this.
Although the Conservatives would have seen the largest net reduction in donations across all the parties, at any level of cap, Labour would have seen the largest proportional reduction in their donations. This is because the Conservatives received donations from a larger number of unique donors than any other party. On average, the Conservatives received donations from 469 unique donors in a year, compared to 172 for Labour.
Figure 2: Number of unique donors per year for the Conservative, Labour, Liberal Democrat, Reform and Green parties over the reporting threshold
| 2020 | 2021 | 2022 | 2023 | 2024 | 2025 | |
|---|---|---|---|---|---|---|
| Conservative and Unionist Party | 428 | 500 | 459 | 535 | 647 | 246 |
| Labour Party | 85 | 152 | 165 | 213 | 310 | 108 |
| Liberal Democrats | 159 | 244 | 279 | 413 | 498 | 277 |
| Reform UK | 4 | 5 | 1 | 5 | 38 | 77 |
| Green Party | 22 | 29 | 38 | 52 | 56 | 30 |
Figure 3: Number of unique donors per year for the Sottish National Party, Co-operative Party, Reclaim Party and Sinn Féin over the reporting threshold
| 2020 | 2021 | 2022 | 2023 | 2024 | 2025 | |
|---|---|---|---|---|---|---|
| Scottish National Party (SNP) | 6 | 12 | 6 | 6 | 13 | 5 |
| Co-operative Party | 8 | 9 | 8 | 11 | 8 | 8 |
| The Reclaim Party | 1 | 2 | 1 | 1 | 1 | 1 |
| Sinn Féin | 2 | 6 | 1 | 3 | 2 | 3 |
| Party | Proportion of donors who donated over £100k | Proportion of donors who donated over £50k | Proportion of donors who donated over £10k |
|---|---|---|---|
| Conservative and Unionist Party | 6% | 13% | 45% |
| Labour Party | 11% | 18% | 51% |
| Liberal Democrats | 3% | 6% | 31% |
| Reform UK | 24% | 40% | 95% |
| Scottish National Party (SNP) | 15% | 21% | 52% |
| Co-operative Party | 23% | 31% | 90% |
| Green Party | 2% | 5% | 25% |
| The Reclaim Party | 86% | 86% | 86% |
| Sinn Féin | 29% | 41% | 76% |
| Other | 5% | 15% | 53% |
Parties who have received standalone large donations in the past five years would have been the most affected by any cap level. The Reclaim Party is the most notable example, as they received all their donations from one individual each year, and so they would have lost just under 90% of their funding at the most generous cap level.
Meanwhile, parties who receive fewer large donations, such as the Liberal Democrats or the Green Party, would have been proportionally less impacted by a cap in comparison to others.
The impact of caps on Conservatives, Labour, Liberal Democrats and Reform
Figure 4 compares the potential impact that different levels of cap would have had on the Conservatives, Labour, Liberal Democrats and Reform. These are the four parties with the highest amount of donations in the last five years. The grey bar shows the amount each party received in donations that year, compared to where that amount would have been with different levels of caps.
It highlights that any level of cap would have resulted in Labour raising significantly less than the Conservatives, even in 2024 when Labour actually raised almost £10 million more. Caps would have brought Labour to a similar level of donation as the Liberal Democrats – who, on average, receive donations from almost double the number of unique donors as Labour.
The chart also highlights that caps would have had a significant impact on donations to the Conservatives. Although the party would have consistently received more than Labour, a £100k cap would have meant a £36 million reduction in funds in 2023.
Reform’s donation profile has changed significantly since 2020. In 2020, the party had four donors who made a reportable donation, compared to 77 in 2025. In 2025, a quarter (25%) of donors donated above £100k.
Figure 4: Impact of different levels of donation cap on the Labour Party, Conservative Party, Liberal Democrats and Reform
| Conservative | Labour | Liberal Democrats | Reform UK | |
|---|---|---|---|---|
| 2020 | £14,910,000 | £6,930,000 | £2,620,000 | £2,060,000 |
| 2021 | £19,480,000 | £9,320,000 | £2,890,000 | £210,000 |
| 2022 | £17,270,000 | £12,900,000 | £4,470,000 | £20,000 |
| 2023 | £47,380,000 | £21,630,000 | £6,580,000 | £260,000 |
| 2024 | £29,140,000 | £37,590,000 | £9,760,000 | £3,040,000 |
| 2025 | £14,020,000 | £9,260,000 | £5,090,000 | £18,630,000 |
| Conservative | Labour | Liberal Democrats | Reform UK | |
|---|---|---|---|---|
| 2020 | £10250000 | £1570000 | £1830000 | £400000 |
| 2021 | £12610000 | £3020000 | £2730000 | £170000 |
| 2022 | £10360000 | £4370000 | £3910000 | £20000 |
| 2023 | £11090000 | £5980000 | £5710000 | £140000 |
| 2024 | £12400000 | £9430000 | £7810000 | £1910000 |
| 2025 | £7490000 | £3690000 | £4730000 | £4100000 |
| Conservative | Labour | Liberal Democrats | Reform UK | |
|---|---|---|---|---|
| 2020 | £8,440,000 | £1,240,000 | £1,600,000 | £200,000 |
| 2021 | £10,020,000 | £2,420,000 | £2,380,000 | £120,000 |
| 2022 | £8,690,000 | £3,350,000 | £3,430,000 | £20,000 |
| 2023 | £8,960,000 | £4,260,000 | £4,830,000 | £90,000 |
| 2024 | £9,740,000 | £6,490,000 | £6,460,000 | £1,340,000 |
| 2025 | £5,770,000 | £2,650,000 | £3,990,000 | £2,620,000 |
| Conservative | Labour | Liberal Democrats | Reform UK | |
|---|---|---|---|---|
| 2020 | £3,510,000 | £603,000 | £960,000 | £40,000 |
| 2021 | £3,890,000 | £1,070,000 | £1,350,000 | £40,000 |
| 2022 | £3,460,000 | £1,300,000 | £1,720,000 | £10,000 |
| 2023 | £3,830,000 | £1,640,000 | £2,560,000 | £50,000 |
| 2024 | £4,470,000 | £2,420,000 | £3,190,000 | £380,000 |
| 2025 | £1,970,000 | £870,000 | £1,900,000 | £740,000 |
The impact of caps on the SNP, Co-operative Party, Green Party, Reclaim Party and Sinn Féin
Figure 5 shows the impact of different levels of caps on five smaller parties across the years(by donation amounts). It highlights that there is no clear pattern of impact of donation caps on smaller parties across individual years.
In general, parties which receive a larger amount of smaller value donations, such as the Scottish National Party (SNP) or the Green Party, would have been the least affected by potential caps. However, there are some years when this wasn’t the case (e.g. 2021 for the SNP, likely due to the Scottish Parliament elections).
Figure 5: Impact of different levels of donation cap on the SNP, Co-operative Party, Green Party, Reclaim Party and Sinn Féin
| SNP | Co-operative Party | Green Party | The Reclaim Party | Sinn Féin | |
|---|---|---|---|---|---|
| 2020 | £210,000 | £814,000 | £242,000 | £196,000 | £120,000 |
| 2021 | £758,000 | £843,000 | £339,000 | £2,003,000 | £847,000 |
| 2022 | £394,000 | £832,000 | £500,000 | £716,000 | £350,000 |
| 2023 | £81,000 | £872,000 | £627,000 | £700,000 | £366,000 |
| 2024 | £953,000 | £1,107,000 | £787,000 | £475,000 | £89,000 |
| 2025 | £52,000 | £934,000 | £388,000 | £180,000 | £380,000 |
| SNP | Co-operative Party | Green Party | The Reclaim Party | Sinn Féin | |
|---|---|---|---|---|---|
| 2020 | £210,000 | £311,000 | £242,000 | £100,000 | £120,000 |
| 2021 | £338,000 | £341,000 | £339,000 | £100,000 | £147,000 |
| 2022 | £248,000 | £333,000 | £472,000 | £100,000 | £100,000 |
| 2023 | £81,000 | £314,000 | £607,000 | £100,000 | £224,000 |
| 2024 | £542,000 | £410,000 | £645,000 | £100,000 | £89,000 |
| 2025 | £52,000 | £394,000 | £388,000 | £100,000 | £142,000 |
| SNP | Co-operative Party | Green Party | The Reclaim Party | Sinn Féin | |
|---|---|---|---|---|---|
| 2020 | £129,000 | £211,000 | £212,000 | £50,000 | £70,000 |
| 2021 | £238,000 | £241,000 | £333,000 | £50,000 | £97,000 |
| 2022 | £156,000 | £234,000 | £351,000 | £50,000 | £50,000 |
| 2023 | £81,000 | £243,000 | £514,000 | £50,000 | £124,000 |
| 2024 | £342,000 | £303,000 | £545,000 | £50,000 | £87,000 |
| 2025 | £52,000 | £287,000 | £362,000 | £50,000 | £92,000 |
| SNP | Co-operative Party | Green Party | The Reclaim Party | Sinn Féin | |
|---|---|---|---|---|---|
| 2020 | £39,000 | £63,000 | £138,000 | £10,000 | £20,000 |
| 2021 | £89,000 | £78,000 | £172,000 | £10,000 | £44,000 |
| 2022 | £40,000 | £80,000 | £220,000 | £10,000 | £10,000 |
| 2023 | £36,000 | £99,000 | £302,000 | £10,000 | £30,000 |
| 2024 | £97,000 | £74,000 | £319,000 | £10,000 | £20,000 |
| 2025 | £25,000 | £80,000 | £207,000 | £10,000 | £30,000 |