Labour's byelection win in Holborn and St Pancras has been followed less by celebration than by recrimination inside the Green party, where leader Zack Polanski is confronting criticism from senior figures and calls for his resignation over his absence from the conference vote on a motion equating Zionism with racism.

Labour claims left-wing voters are returning

The party's deputy leader, Lucy Powell, said the result shows Labour is starting to win back voters on the left who became disillusioned under Keir Starmer's leadership. Sagal Abdi-Wali took 45% of the vote on a relatively low turnout to hold the north London seat, pushing Polanski, who stood for the party he leads, into second place on 33%.

Powell told the Guardian after the win that the result "sends a clear message to those voters who lost faith in Labour in recent years". Last month she had called for the party to unite progressive voters under Andy Burnham to win the next election.

Labour strategists were buoyed by a relatively straightforward route to victory in a diverse inner-city area, the kind of seat the Greens have targeted with recent success.

Polanski criticised for missing the Zionism debate

The contest was fought in the shadow of the Green party conference voting the previous weekend to adopt a policy equating Zionism with racism and saying Israel should be replaced with a single Palestinian state.

Polanski missed the debate because he was campaigning in the byelection, and critics accuse him of abdicating leadership by giving no clear message about whether he backed the motion. He said after the loss that he would have voted against it had he attended, because two amendments he supported - stating that a Palestinian state's future structure should be decided by Palestinians rather than imposing a one-state system - were voted down.

Caroline Lucas, the party's former leader and first MP, said Polanski "should have been there and he should have voted", and told Newsnight that in her view "the motion was flawed from top to bottom".

Resignation call and party splits

Vivien Lichtenstein, chair of Jewish Greens, said Polanski, who is Jewish, made a "big mistake" by avoiding the vote. Asked on Friday whether he should continue in his role, she told Times Radio: "No, I think he should resign."

The call did not go unchallenged within the party. Other Jewish Greens members said Lichtenstein's comments did not reflect the majority view, and a vote of no confidence in her had been tabled. Asked whether Polanski should stand down, Lucas did not say definitively that he should remain, replying: "I think let's just see what happens in the … coming days and weeks."

Second-best Green result and what comes next

Despite the backlash, the byelection marked the Greens' second best-ever result, evidence the party has grown more prominent since Polanski became leader 13 months ago. He said the outcome showed the Greens remained a major threat to Labour, but that many voters told him they wanted to "give Andy Burnham a chance".

• •The Greens' best byelection result came in February, when they took the safe Labour seat Gorton and Denton in Greater Manchester in a major upset, weakening Starmer's position.
• •Around that time the party peaked at 21% in national polling, above Labour; it now stands at about 11%, more than 15 points behind Burnham's party.

Polanski faces re-election by party members in less than a year. There is no formal mechanism for ejecting a Green leader, but leaders stand again every two years, and with Polanski having taken over in September 2025, members will get their verdict at the next contest.