Nearly half of Labour voters say they would consider voting for the Greens at the next election, a poll has revealed.

According to Opinium, 47% of Labour supporters say they would be open to voting for the Green Party, while 21% said they would consider Reform UK.

The survey also found that Keir Starmer’s approval rating has hit a record low, with just 15% of respondents approving of his leadership, giving him a net score of -49. The figure is lower than that of Theresa May, Boris Johnson, or Rishi Sunak at the least popular points in their premierships.

This poll follows Labour’s crushing defeat in the Gorton and Denton by-election earlier this week, where the Green Party captured a seat it had never won before. Labour, which had held the constituency since 1931, finished third behind both the Greens and Reform UK. The party’s vote share of 51% in 2024 dropped to just 25% in the by-election.

The by-election result has intensified scrutiny of Starmer’s leadership, amid growing dissatisfaction within his party. The contest was also clouded by allegations of “family voting,” with Democracy Volunteers reporting that 12% of observed voters appeared to be influenced by a relative when casting their ballot.

Further polling from Opinium in the run-up to the by-election showed that Labour support was drifting to the Greens. A poll conducted in Gorton and Denton showed that 17% of those who voted for Labour in 2024 would vote for the Greens in the by-election.

The poll also indicated volatility among Conservative voters: 42% said they might consider voting for Reform UK. Conservative leader Kemi Badenoch’s net approval rating stands at -8, while Liberal Democrat leader Ed Davey recorded the highest net approval among major party leaders at -5.

Among those leaning Green, climate change and environmental concerns were cited as key motivators. Reform UK supporters highlighted immigration and border control as their primary issues.

James Crouch, head of policy and public affairs at Opinium, said the figures underscored “just how shaky Labour’s ground has become,” adding that both Labour and the Conservatives “looked more fragile than ever”.