Five Labour councillors on Brent Council in north-west London have resigned from the party and joined the Green Party, in a fresh setback for Prime Minister Sir Keir Starmer as Labour faces mounting pressure on its left flank ahead of next year’s local elections.

Green Party leader Zack Polanski, speaking at an event in Wembley on Monday evening to welcome the councillors, said Labour was “broken” and claimed the Greens were ready to “bury” the party at the 2026 local elections.

The move creates Brent’s first Green group on the council, in an area where Labour has traditionally dominated local politics. It also comes amid a rapid increase in Green Party membership under Polanski’s leadership and a series of smaller Labour-to-Green defections elsewhere in London in recent months.

Those defecting are Harbi Farah, a former cabinet member on the council, and Iman Ahmadi‑Moghaddam, a former Labour group whip, along with Mary Mitchell, Tony Ethapemi and Erica Gbajumo.

Several of the councillors had been deselected as Labour candidates earlier this year as the party began selecting its slate for the 2026 local elections. Labour said those who were not selected had failed to meet party standards.

Farah and Ahmadi‑Moghaddam are among a group of councillors in Brent who were barred from standing again, a decision that prompted local controversy and claims by critics of increased central party control. Labour has not accepted the characterisation of the process as a “purge” and has defended its selections as transparent and rigorous.

At the Wembley event, Polanski welcomed the councillors and argued that Labour had moved away from progressive politics. “I think they are broken, and I think we’re ready to bury them,” he said.

Mitchell said the group felt unable to continue representing their communities as Labour members and accused the Government of drifting from Labour’s traditional values. “We always knew that being a party of government would put the principles and values of the party to the test,” she said, adding that ministers had moved away from “democracy, social justice and equality”.

In separate remarks reported from the event, Ahmadi‑Moghaddam criticised Labour’s approach to austerity, housing and migration, and referred to the war in Gaza. His comments, including his characterisation of Israel’s actions, were strongly contested language presented as his view, not an established legal finding.

Farah said she joined Labour for “social justice and equality” but had become increasingly disappointed, adding: “My values have not changed, the party has.”

A Labour spokesperson said: “All but one of the individuals unveiled were not selected to stand for the Labour Party. They fell below the standards we require of those seeking to represent Labour.”

A London Labour spokesperson also criticised the Greens’ decision to accept the defectors, saying: “The Labour Party operates rigorous and transparent selection processes and maintains the highest standards for its candidates. Mr Polanski’s approach suggests a far lower bar for entry.”

The spokesperson added Labour would contest the 2026 local elections on what it described as a “proud record of delivery”, and said Brent’s Labour-run council was working with a Labour mayor and a Labour national government on priorities including affordable housing and local investment.

Brent Council was last contested in 2022, when Labour won 49 of 57 seats, with the Conservatives on five and the Liberal Democrats on three. The Greens won no seats at that election. The five defections reduce Labour’s numbers but do not threaten its overall control of the authority.

The defections come as the Green Party says its membership has surged since Polanski became leader in September, rising from about 70,000 to more than 180,000. The party has sought to turn that growth into local and parliamentary gains, particularly in London and other urban areas where Labour has historically been strongest.

Polanski played down speculation that Labour MPs could follow councillors in leaving the party, saying his focus was on winning seats rather than attracting defectors. The next electoral test for both parties will be the London borough elections in May 2026, where Labour will be defending large majorities across the capital and the Greens will be seeking to translate membership momentum into votes.