Sadiq Khan urges Labour to stop assuming support from progressive voters.

London’s mayor has warned that the Gorton and Denton by‑election has revealed a “wide‑reaching shift and division” in British politics and that Labour must abandon its “defective approach” of assuming liberal progressives will stay loyal.

In what reads as a rebuke of Keir Starmer, Sadiq Khan disputed the prime minister’s description of the Green Party and its platform as “radical”, noting that many of its backers share Labour’s principles but are disillusioned with the government.

Plumber Hannah Spencer overturned a Labour lead of over 13,000 votes to become the Greens’ fifth MP. Under the new leadership of Zack Polanski, the party has seen its popularity rise, drawing numerous dissatisfied former Labour voters.

Labour’s contender, Angeliki Stogia, finished third, just behind Reform UK’s Matt Goodwin, delivering one of the most embarrassing by‑election outcomes in the party’s record.

Party insiders have long cautioned that Labour risks losing its left‑wing base as it seeks to counter the surge of Reform UK.

Polanski has attacked Labour’s recent tough immigration stance, accusing the party of echoing “the racist language of the far right”. Home Secretary Shabana Mahmood is expected to reinforce the plan with further asylum‑policy changes.

Writing for CuriosityNews, Khan argued that trying to match Reform is unauthentic and betrays Labour’s core values, warning that the party could face disaster in the May polls unless it alters its course.

Khan said: “There is no sugar‑coating of what occurred in the Gorton and Denton by‑election – it is a poor result for Labour, finishing third in a seat we held for almost a century.

“Analysts often overstate the importance of by‑elections, but this one signals a wide‑reaching shift and division in our politics that cannot be ignored or dismissed.

“A strategy that takes liberal, progressive voters for granted is plainly flawed. The national Labour party and government must not only reflect on this outcome but fundamentally rethink its approach.”

While stopping short of demanding Starmer’s resignation, Khan criticised the prime minister for labeling Green voters as extreme in light of the loss.

“The great majority of those considering a Green vote are not extreme,” Khan said. “Many share our aspirations for the country but are disappointed with the government. Branding them extreme will only push more people away.

“The danger to Labour is now existential in parts of the nation. Without a course correction, we risk repeating the loss of major Labour strongholds, such as London, as we did in the 2000s in Scotland,” he added.

“If we fail to unite progressives, we open the door to the darkness and division of Reform – a party that looks to Donald Trump for inspiration and has pledged an ICE‑style force on Britain’s streets, a prospect that chills every minority community here.”