The Green Party of England and Wales won four Westminster seats at the 2024 general election, its best result. Siân Berry held Brighton Pavilion; Carla Denyer took Bristol Central from Labour, unseating the shadow culture secretary Thangam Debbonaire; Adrian Ramsay won Waveney Valley and Ellie Chowns North Herefordshire, both from the Conservatives. In February 2026 the party won the Gorton and Denton by-election, taking a long-held Labour seat and bringing its group to five, up from a single MP two years earlier.
The leadership changed shape in September 2025, when Zack Polanski, the deputy leader, won with 84.6 per cent against a joint ticket of Ramsay and Chowns, the largest mandate in the party's history. Polanski is not an MP; he leads from the London Assembly, where he has sat since 2021, and he is the party's first Jewish leader. Caroline Lucas, the Greens' best-known figure, backed his opponents. The membership chose the insurgent.
Under Polanski the party's growth has outpaced any rival. Membership rose from around 68,000 at his election to more than 226,000 by April 2026, overtaking both the Conservatives and the Liberal Democrats to make the Greens the third-largest UK party by membership, and national polling moved into the mid-to-high teens. His contribution has been less to the policy programme, which is largely unchanged, than to its framing: the sprawling 2024 manifesto, forty billion pounds of annual investment, a wealth tax, seventy per cent wind by 2030, free social care, rent controls, proportional representation, votes at 16 and Palestinian recognition among it, has been narrowed in public to three lines, tax wealth, stop arming Israel, act faster on climate. The rest remains party policy; those three have become the identity.
What the growth has not yet produced is parliamentary weight. The five-MP group tables amendments but does not set the terms of debate; Labour controls the argument on 2030 clean power, and the Greens have not forced a reckoning over the gap between Labour's climate targets and its delivery. The manifesto's 150,000 social homes a year has not become a leading campaign, and the party's oldest cause, proportional representation, has been left to others. The welfare headline the Greens shared, scrapping the two-child benefit cap, was delivered by Labour's November 2025 Budget. On Gaza, Polanski has gone beyond the manifesto's call for recognition and an arms embargo, telling a London march that "our government is not just complicit but active participants"; Labour recognised a Palestinian state in September 2025, but Parliament has not adopted the embargo.
The growth has also brought a problem the leadership has not contained. Ahead of the 2026 local elections the party was caught in an antisemitism scandal reported across the Jewish and national press: Newcastle Greens withdrew their endorsement of two candidates, Philip Brookes and Mohammed Suleman, over antisemitic social-media posts, Suleman having reposted a video claiming Jewish prisoners willingly buried Soviet prisoners of war alive under Nazi orders; both were placed under a national disciplinary process, and other candidates faced similar action, including two in London arrested on suspicion of stirring up racial hatred online. Polanski called the material "unacceptable" and promised a standard vetting process and compulsory training, but some candidates were not removed before polling day. Managing a repeated candidate-vetting failure of this kind is the sharpest tension of his first months in charge.
The local results were the party's best, with more than 1,300 councillors now elected across England, and Gorton and Denton showed the Greens can win in Labour's old industrial areas, not only in university cities and the affluent south. But the structural problem is the mirror image of Reform's: the Green vote is spread across student towns, inner cities and suburban progressives, which wins councils but rarely wins Commons seats, while Reform's is concentrated where it can. On roughly a mid-teens national share the Greens hold well under one per cent of Westminster seats. The next test is whether a movement this large can turn into more than five votes in a chamber it cannot yet move, or whether the membership and the seats stay as far apart as they are now.