How EU policy affects Labour’s electability

IMPACT ON PROPENSITY TO VOTE, AND PERFORMANCE IN LABOUR MANIFESTOS

Executive Summary

The report finds that all EU relations policy options beyond the UK Government’s current red lines are likely to increase the electorate’s openness to voting Labour, by varying amounts. 

Across all respondents, propensity to vote Labour increased the most – by seven percentage points – in a scenario where it pledged to make the UK a member of the EU. This finding and conclusion was consistent with previous Best for Britain research, which found EU membership to be the most popular EU relations policy among both voters in general, and Labour’s voters at the 2024 General Election in particular. 

Analysis of Labour’s defectors since the 2024 General Election strongly suggests that a policy of full EU membership should be the cornerstone of any attempt to rebuild Labour’s electoral coalition ahead of a General Election. 

A pledge to full membership of the EU significantly increased propensity to vote Labour among Labour’s defectors to the Liberal Democrats, the Scottish National Party, Plaid Cymru, but especially its defectors to the Green Party. 

All EU relations policy positions increased propensity to vote Labour among Labour’s 2024 voters who would now stay at home and not vote at all. However, only a policy of EU membership reduced this important group’s likelihood of voting for the Green Party in future. 

The motivations behind Labour’s 2024 electoral coalition came across clearly. A majority of all Labour Supporters and defectors to its left flank fail to identify any drawback of the UK becoming a member of the EU again, as did a third of Labour’s defectors to Reform UK and the Conservatives. They identified improving trade and the economy, and a return to Freedom of Movement as the main benefits of EU membership. 

Reform UK and Conservative Supporters continued to identify sovereignty as the main drawback of EU membership, followed by the associated costs. Immigration appeared to have reduced in salience as a concern for this group of voters. 

Either way, Reform UK and Conservative Supporters continued to appear as an intractable group of voters for Labour. No Labour EU relations policy position, including a policy of further loosening ties with the EU, increased their propensity to vote Labour. 

On the left of UK politics, this report finds a significant vulnerability in both the Liberal Democrat and Green Party policy positions on EU relations. 

The report identifies double-digit increases in propensity to vote Labour, even where Labour were to pledge to join a Customs Union, among both Liberal Democrat and Green Supporters overall. With propensity to vote Labour increasing by 21 and 18 percentage points among Liberal Democrat and Green Supporters respectively where Labour offered EU membership, this suggested both Liberal Democrats and the Green Party policy offers on EU relations were only sustainable where Labour remains committed to its red lines. 

Indeed data in this report showed that both an overt commitment to make the UK a member of the EU, or a commitment to ‘explore all options for closer EU relations including membership of the EU’ increased the popularity of a hypothetical Labour manifesto in manifesto  mockups. 

The inclusion of a commitment to EU membership in Labour manifesto mockups was an effective way to draw the support of all Labour’s defectors to parties on its left flank, Labour’s current supporters, and current supporters of the Liberal Democrats and Green Party in general. 

Taken together, the increase in propensity to vote Labour across all its defector crossbreaks, and popularity of Labour manifestos which included a commitment to EU membership, suggest that a Labour Party policy of EU membership will be essential to rebuilding its 2024 electoral coalition, and would significantly improve Labour’s electoral performance at any future General Election. 

Headline findings

1. All EU relationship options beyond the UK Government’s current negotiations red lines increased respondent’s propensity to vote Labour. Moving to a policy of full EU membership resulted in propensity to vote Labour to increase by seven percentage points across all GB adults.
2. Moving beyond the UK Government red lines on EU relations significantly increased propensity to vote Labour among Labour Left Defectors. A policy of membership of the EU was most likely to appeal to Labour Left Defectors, increasing their propensity to vote Labour by 14 percentage points.
3. Propensity to vote Labour among Liberal Democrat and Green Party Supporters increased by 21 and 18 percentage points respectively, where Labour pledged to pursue membership of the EU.
4. Including a commitment to EU membership in Labour manifesto mockups significantly increased the popularity of the Labour manifesto. A manifesto commitment to exploring all options for closer EU relations, including EU membership, had a slightly broader appeal within Labour Defector crossbreaks.

How EU policy affects Propensity to Vote

Results clearly showed that the more ambitious Labour’s EU policy position on EU relations, the higher the absolute propensity to vote Labour across the entire sample. Propensity to vote measures openness to voting for a party (rather than a forced single choice through voting intention). Respondents can say they are likely to vote for multiple parties.

Between commissioning the survey and publishing this report, the Labour Party changed Party Leader and Prime Minister. Subsequent public opinion polls suggested a change in Westminster voting intention since commissioning the reported results. It is therefore likely that the absolute propensities to vote for each party will have also changed. However, the relative changes in propensity to vote for the different parties based on Labour’s EU policy position compared to the selected control group baseline are unlikely to have been affected by the change of Labour leader. 

All EU relationship options beyond the UK Government’s current negotiations red lines increased respondent’s propensity to vote Labour. Labour moving to a policy of full EU membership resulted in the most significant change in propensity to vote Labour, rising seven percentage points above the baseline.

Labour’s left defectors 

Among respondents who voted Labour in 2024, and have since switched allegiance to the Lib Dems, the Green Party, the SNP or Plaid Cymru, a pledge to EU membership increased their likelihood to vote Labour by twice the average (14% points above the baseline) – while Labour to Green Party switchers alone recorded a 16% point increase in likelihood of supporting Labour again. Willingness to vote Labour among current Lib Dem and Green Party supporters overall increased by 21 and 18 percentage points each, based on a Labour EU membership pledge.

Overall, Labour’s position on Europe had a greater influence on Liberal Democrat and Green Party Supporters than on any of the Labour Defector groups analysed in this report. This suggested that Labour’s approach to EU relations was particularly important in shaping the voting intentions of pro-European party supporters. Though not tested in this survey, it is reasonable to expect that supporters of other strongly pro-European parties, such as the Scottish National Party (SNP) and Plaid Cymru, would respond in a similar way. 

Labour to Green Defectors’

Among Labour to Green Defectors, propensity to vote Labour rose by 16 percentage points, compared with 14 points among Labour Left Defectors overall, were Labour to adopt a policy position of membership of the EU.

Labour Non-Voters

Labour Non-Voters (defined as respondents who voted Labour in 2024 and now say they either ‘do not know’ how they would vote or ‘would not vote’) only considered returning to Labour or switching to the Green Party. They showed no meaningful propensity to vote for any other party.

Liberal Democrat and Green Supporters overall

Overall, Labour’s position on Europe had a greater influence on Liberal Democrat and Green Party Supporters than on any of the Labour Defector groups analysed in this report. This suggested that Labour’s approach to EU relations was particularly important in shaping the voting intentions of pro-European party supporters. Though not tested in this survey, it is reasonable to expect that supporters of other strongly pro-European parties, such as the Scottish National Party (SNP) and Plaid Cymru, would respond in a similar way. 

The EU membership scenario produced a dramatic increase in Labour’s appeal among Liberal Democrat Supporters, increasing their propensity to vote Labour by 21 percentage points. 

This was the largest shift recorded against the baseline of any subgroup analysed in this randomised control trial.

Regardless of Labour’s position on Europe, Green Supporters only considered voting Green or Labour, with very small changes in propensity to vote for the remaining three parties. 

Both the Customs Union and Single Market scenarios were equally effective at attracting Green Supporters, increasing their propensity to vote Labour by 13 percentage points compared with the baseline. 

Conservative and Reform UK Supporters

Among Conservative and Reform UK supporters, the polling found no evidence that any Labour policy pledge on the EU increased their likelihood to vote for the party – even where Labour pledged to further loosen ties with the EU. Analysis suggests these groups remain firmly “intractable” for Labour, with attempts to persuade them looking increasingly unlikely to succeed.

Changes in Labour’s position on Europe produced only minor shifts in both groups’ propensity to vote Labour – all within the statistical margin of error.

How Labour’s EU policy position fares in a manifesto context

The study also found that including a commitment to EU membership in hypothetical future Labour Party manifestos drastically increased the likelihood of voters choosing it. Where a hypothetical manifesto included a promise to explore all options for closer EU relations, including full membership, it successfully maintained the support of Labour’s 2024 coalition, and even broadened its electoral appeal. Among voters who have lost faith in Labour since 2024 but remain within the progressive ‘left-bloc’, the most popular manifesto policy was to explicitly commit to EU membership.

The survey results suggest that the UK Government’s incremental approach to EU relations appeals most to Conservative and Reform UK Supporters, who were more likely to choose EU policies within current UK Government red lines. However, these groups do not appear to be willing to vote Labour, even as it pursues their preferred approach.

A note on interpreting the results. 

Figures reported are the probability that a policy was in the manifesto the respondent chose, across all the occasions it was shown. The results therefore represent the relative appeal of the policy within the experiment, not the share of respondents  supporting the policy. Because respondents could also select ‘Neither’, the results are not centred on 50% as would be the case in a straight two-way choice.

On average ‘Neither’ was selected 45% of the time, which is expected given the number of respondents who would not consider supporting a Labour manifesto under any circumstance.  Since each respondent was shown ten distinct policies with five of them in the chosen manifesto whenever a choice was made, the average probability of selection across the full pool of 27 policies was 27.5%.

Therefore it is this figure of 27.5%, not 50%, against which individual policies should be judged. This means that any policy with a probability of being chosen above 27.5% was more popular than the average policy, whereas any policy with a probability of being chosen below 27.5% was less popular than the average policy.

Methodology

All figures, unless otherwise stated, are from YouGov Plc. The total sample size was 10,324 adults. Fieldwork was undertaken between 29th April and 5th May 2026. The survey was carried out online. The figures have been weighted and are representative of all GB adults (aged 18+).

Both surveys were conducted using an online interview of members of the YouGov Plc GB panel of 400,000+ individuals who have agreed to take part in surveys. An email was sent to panellists selected at random from the base sample according to the sample definition, inviting them to take part in the survey and providing a link to the survey. 

YouGov Plc normally achieves a response rate of approximately 20% depending on the subject matter, complexity and length of the questionnaire. The responding samples were weighted to the profile of the sample definition to provide a representative reporting sample. The profile is normally derived from census data or, if not available from the census, from industry accepted data.  

The report presents three polling surveys, conducted by YouGov on behalf of Best for Britain. The first experiment identified how Labour’s policy position on EU relations affected propensity to vote Labour. The second survey was a conjoint experiment, where respondents were shown two hypothetical Labour Party election manifestos containing a list of five policies, drawn at random from a pool of 27, including one EU related policy drawn from a list of 11. These included EU policy positions ranging from further loosening ties with the EU to full membership of the EU, including a UK-EU Customs Union and Single Market membership, without a return to full membership of the EU. Lastly, the report presents respondent’s views on the potential benefits and drawbacks of UK membership of the EU. Respondents answered these questions in their own words, which YouGov’s AI model grouped into categories.