Sagal Abdi-Wali, the leader of Camden council, successfully defended the seat previously held by Sir Keir Starmer after the former prime minister quit last month.

She won with 12,292 votes to Mr Polanski’s 8,928.

Conservative Ewan Cameron came in third.

Accepting her victory, Ms Abdi-Wali thanked her predecessor Sir Keir and said she was proud to be the first woman to represent the constituency.

She added: “In Camden our diversity is a strength and our cohesion has been too hard won to take for granted.

“Since I was a child, I have watched people across Camden work to build communities where difference is not something to fear but something to value.

“We cannot allow that work built over generations to be casually undone by those who seek to divide us.”

Ahead of the official declaration, the Greens conceded defeat.

A party spokesperson said: "It is clear now we will come a close second in this by-election.

“Taking the fight to Labour in one of its safest seats shows just how far the Greens have come. Voters want us to keep Labour’s feet to the fire on affordable housing, public ownership of water and the climate crisis.

“Greens will be there every single day, holding Labour to account and demanding the change people voted for."

The Greens put huge effort into defeating Labour, mobilising dozens of campaigners in the streets of north London in the lead up to the poll.

It followed a last-minute appeal from Mr Burnham the same morning, encouraging Londoners to vote for “hope”.

Labour’s efforts follow a tough week for Mr Polanski.

A controversial motion, which asserted that “Zionism is racism”, was passed at the party’s annual conference in Brighton, sparking backlash and damage to approval ratings.