Andy Burnham is set to become the UK's new prime minister on Monday, July 20, 2026, replacing Keir Starmer. But in the four days before he takes office, Green Party leader Zack Polanski is launching a flood of media attacks against him. The Greens want to push back against the idea that Burnham will be much more left-leaning than Starmer, according to The Guardian.

Polanski's main argument is simple: he says Burnham is too close to big business and corporate interests to actually deliver change. "Andy Burnham is too in hock to vested interests to offer real change," Polanski said. On July 16, he posted on X that Burnham's reported choice of Shabana Mahmood as chancellor (the government's top finance role) rather than Ed Miliband showed he was "subservient to the City of London." The City of London is the UK's financial district, and saying someone is "subservient" to it means they are too willing to please banks and financial firms. The Guardian had reported on July 15, 2026 that Burnham planned to give Mahmood the Treasury. This is not a new attack: Polanski used almost the same language back on October 3, 2025, when he told a Guardian live blog that the UK political class is "poisoned by wealth" and linked Burnham to being "in hoc to vested interests." He repeated the phrase on BBC Radio 4 and on Instagram in late June 2026.

The Greens have given Burnham a nickname: "semi-skimmed Andy." The idea is like the difference between semi-skimmed and full-fat milk. Semi-skimmed looks like the real thing but has had something removed. The Greens are saying Burnham talks like a left-wing politician but waters down his policies, while the Greens offer the "full-fat" version. The specific policy gaps they are pointing to are real. As mayor of Greater Manchester, Burnham supported rent controls, but he has not promised them as prime minister. He has talked about "public control" of the water industry rather than taking it fully into government ownership. He told reporters he had "something of an open mind" on allowing more oil and gas drilling in the North Sea. He ruled out changing the voting system to proportional representation — a system where the number of seats a party gets in parliament matches its share of the vote — until after the next general election. On Gaza, Burnham apologised for Labour's initial response under Starmer to Israel's military action, but he has not gone as far as the Greens, who want a total ban on UK arms sales to Israel and broader sanctions, which are government-imposed penalties meant to pressure a country into changing its behaviour.

Polanski has been building toward this fight for months. On January 25, 2026, the Green Party published his statement claiming the Greens were "the only progressive party capable of taking on" Labour in the Gorton and Denton by-election, after Burnham was blocked from standing there. On June 24, 2026, Polanski called Burnham's plan to hire a top lobbyist a "Blair tribute act" in openDemocracy, comparing him to former prime minister Tony Blair. The next day he posted on Instagram: "The jury's out on Andy Burnham." On July 7, he published a press release challenging Burnham to say whether he would end Britain's role in what the party called "1,000 days of genocide in Gaza." Two days later the party launched a manifesto with the slogan "take back Greater Manchester from big money." On July 10, Reuters covered Polanski's challenge to Burnham to implement rent controls. On July 12, he posted on Instagram that he would not rule out a deal with Burnham, but that immigration policy and Palestine would have to be agreed first. On July 14, he posted an image with the text "Same old Labour. Then. Now. Forever."

These attacks carry more weight than they would have a year ago. Under Polanski's leadership, the Green Party in England and Wales has more than tripled its membership. The Greens are now running close to Labour in opinion polls, and much of their new support comes from people who used to vote Labour but are unhappy with Starmer. Starmer himself acknowledged the threat on April 5, 2026, when he attacked the Greens and warned that voting for Labour's rivals could put new workers' rights at risk. He reportedly saw Polanski's populism as a threat.

The Greens back up their policy attacks with their own polling numbers. They say 81% of people who voted Labour in 2024 support a separate tax on wealth. Polanski called for taxes on the super rich and for utilities like water and energy to be publicly owned, in his June 22, 2026 reaction to Starmer's departure, published by Left Foot Forward. Burnham, who returned to parliament in June 2026 by winning the Makerfield by-election, has not gone that far.

Polanski describes the situation in urgent terms. He said the UK was "at breaking point" because of high rents, water bills, extreme heat, and anger over Gaza. The media blitz before Burnham enters 10 Downing Street is designed to make sure that from the very first hours of his time as prime minister, the Green Party's criticism is part of the conversation, alongside the expected Labour message of renewal.

What we don't yet know is whether Polanski's conditions for working with Burnham — especially on Palestine and immigration — are a real opening for the two parties to cooperate in parliament, or just a way of showing how far apart Labour and the Greens really are. Burnham has not responded to the conditions publicly. The Greens' strategy depends on two things: keeping their polling numbers close to Labour's, and whether the "semi-skimmed" label sticks to a man who has not yet had a chance to govern. The next general election, whenever it happens, will be the real test of whether the voters who left Labour for the Greens under Starmer stay with the Greens or come back to Labour under Burnham.