UK PM Keir Stormer suffered a blow as the Greens won the Gorton & Denton by-election

British Prime Minister Keir Stormer suffered another blow to his leadership on Friday after the left-wing Green Party won a special election the ruling Labor Party has dominated for decades.

The result at Gorton and Denton in Greater Manchester is likely to heighten speculation about the position of Stormer, who has come under pressure from appointing Peter Mandelson as US ambassador despite his association with Jeffrey Epstein and made a series of exits from Downing Street.

Green Party candidate Hannah Spencer received 14,980 votes, or 40.7% of the vote, marking the party’s first by-election victory.

The far-right Reform UK party came second with 10,578 votes on 28.7%, while Labor came third on 25.4% with 9,364 votes.

British government bond yields, known as gilts, edged lower on the news, erasing earlier gains. The 10-year gilt yield stood at 4.267% on Friday morning, while the 30-year gilt yield was last seen at 5.069%.

Spencer, a 34-year-old plumber and plasterer, is the fifth sitting Green lawmaker in Britain’s 650-seat House of Commons.

“Instead of working for a good living, we are working to line the pockets of billionaires. We are anemic and I don’t think it is extreme or radical to think that working hard should get you a happy life,” he said in his victory speech.

Labor won the seat of Garton and Denton at the national general election in July 2024 with nearly 51% of the vote, Starmer came to power and ousted the Conservative Party after 14 years.

In an interview with the broadcaster, Starmer described the result as “very disappointing” and said he understood voters were “frustrated” and “impatient for change”.

The change in the ruling party’s fortunes suggests voters are willing to look beyond the main parties of Labor and the Conservatives or the Tories to alternative parties such as the Greens and Reform UK in May’s wider local elections.

John Curtis, a leading political scientist and professor of politics at the University of Strathclyde in the UK, said the result showed a challenge for the two main parties.

“We’re getting an unprecedented challenge through reform that is, from the right, stroking the more socially conservative end of Britain, challenging the Conservative Party. And now, the Greens are clearly now serious contenders with Labor for voters on the left and more socially liberal minded,” Curtis told Europe on Friday.

“Historically, in Britain, we’ve won elections and said we’ll lose at the centre. That’s not what’s happening at the moment,” he said.

“The Green Party will be completely cock-a-hoop,” Damian Lyons Lowe, CEO of London-based polling company Servation, told CNBC’s “Europe Early Edition” on Friday.

“I think people are looking forward to the local elections now, of course it’s a real energy boost for the Green Party because of the wasted vote argument which is often the bane of the Green Party – a vote for the Greens is allowing for reform, for example, or the Tories,” Lowe said.

“I think those voters will feel energized and the Greens will do better than they did in the local elections in May,” he said.