Labour candidate Sagal Abdi-Wali won Holborn and St Pancras with 12,292 votes, ahead of Green Party leader Zack Polanski on 8,928. The by-election was an early test for Andy Burnham's government after Keir Starmer left Parliament.
The official count published by Camden Council confirmed Abdi-Wali's victory and a majority of 3,364. Turnout was 38.76%. The seat became vacant after Starmer stepped down as an MP in September, two months after leaving the premiership.
Polanski said he would remain Green Party leader and described the result as part of a “honeymoon” for Burnham. He urged the party to focus on challenging the government and on its budget, due to be presented on October 28.
The by-election came amid debate within the Green Party after its conference adopted a motion defining Zionism as a form of racism and calling for a single Palestinian state. Several prominent party figures had criticised the move. Former leader Caroline Lucas told the BBC after the vote that she wanted Polanski to show leadership that, in her view, had been missing during the motion's debate.
The win strengthens Labour's position among left-of-centre voters in London after the Green Party made gains in May's local elections. But a result in one constituency does not measure national opinion. Abdi-Wali, who previously led Camden Council, said after her victory that she now had to deliver on her campaign promises.