Green Party leader Zack Polanski has accused Andy Burnham's government of "an astonishing dereliction of duty" over its response to the UK's record-breaking heat summer, telling a Westminster press conference that ministers had produced "no emergency briefings, no new plan and precious little detail" on how they intend to protect the public.

Speaking at Church House in Westminster on Wednesday, Polanski described the climate crisis as "the biggest threat to this country since the Second World War" and said he was delivering a "reality check" to the new prime minister, who took office on 20 July. He said the government's approach amounted to a decision "to pretend none of this is happening".

The intervention is the Greens' first sustained assault on Burnham since he entered Downing Street, and it arrives at a decision point rather than a rhetorical one. Consultations on the Rosebank and Jackdaw oil and gas fields close this month, leaving ministers to determine whether the projects proceed — the issue on which Polanski chose to challenge the prime minister most directly.

Addressing Burnham by name, Polanski called on him to rule out expansion in the North Sea, insisting on "no new drilling" at either field. Development at both sites was approved under existing licences by a previous government, but the courts overturned those consents and required fresh environmental assessments covering downstream emissions. The government has conceded in court that Rosebank's approval was unlawful because the assessments excluded the climate effects of burning the oil and gas extracted.

Burnham has said he would take "a pragmatic approach" and was "open minded" about expanding drilling, adding: "There is a resource there." His comments followed a claim by US President Donald Trump that Burnham had told him he would "open up North Sea oil". Defence Secretary Wes Streeting has also publicly backed expansion, including at Rosebank. The decision falls to Energy Security and Net Zero Secretary Miatta Fahnbulleh.

Polanski framed the argument in national security terms, saying: "You cannot defend a nation if you refuse to acknowledge the very force that makes its infrastructure obsolete."

"It is an astonishing dereliction of duty from those whose very first responsibility is to keep all of us safe."

He also criticised media coverage, arguing there had been more clamouring for North Sea drilling in recent weeks than alarm-raising about climate breakdown, and said the government had been "far, far too quiet" compared with the public response.

Polanski set out three asks. The first was immediate heat protection, including "a free, accessible cool space in every local area" and financial support for households to heatproof their homes. The second was a "robust wildfire prevention strategy" and a properly resourced fire service, including firefighting helicopters "where needed" — a measure he said would avoid a repeat of a charity contracting a private firm to help fight fires. The third was renationalisation of water, which he linked to securing supply, preventing drought and protecting the food system.

The fire service and heat measures would be funded, he said, by taxing fossil fuel companies "profiting from fuelling these infernos". Party press material framed the speech as a call "for fossil fuel giants to pay cost of adapting to extreme weather and fire risk".

The Green Party has not published costings for the cool spaces, heatproofing grants or helicopters, nor an estimated yield from the proposed levy.

The speech came at the end of a heat health alert during the fourth heatwave of the summer, with roughly half of England officially in drought. Polanski warned that current conditions are "likely some of the least extreme summer temperatures we'll experience in our lifetimes" and that "this is only a taster of what's to come if we don't act now".

He said almost 3,000 people had died from the effects of extreme heat this summer, with older people and those with pre-existing conditions worst affected. That figure is a party estimate. Researchers at Imperial College London, the Met Office and the London School of Hygiene and Tropical Medicine estimated around 550 excess deaths during the May heatwave and about 2,200 during the June event in England and Wales — roughly 2,750 in total for those two episodes alone. The UK Health Security Agency has said it "is likely that 2026 could see the highest number of heat-associated deaths on record", surpassing 2022.

The Met Office recorded a new May national record of 35.1°C in west London on 26 May, followed by three consecutive record June days culminating above 37°C in East Anglia. A reading of 35.2°C at Writtle in Essex was the seventh day of 2026 at 35°C or above; the previous record was five, set in 1976 and matched in 2020. A third heatwave peaked at 35.5°C at Wisley, Surrey, on 9 July, and a fourth began on 28 July, prompting an amber heat-health alert for London, the East Midlands, the East of England and the South East on 29 and 30 July.

Network Rail imposed emergency speed restrictions and timetable changes across southern and eastern routes from 3 August. Fire crews have spent days damping down peat fires to prevent re-ignition, including at Dunwich Heath in Suffolk, where the local fire and rescue service said Sizewell B was not at risk but described "a live and dynamic situation". Other wildfire sites this summer include Headon Warren on the Isle of Wight, Llanwonno in the Rhondda and the Cairngorms National Park.

Polanski's central procedural claim finds some independent support. The Climate Change Committee and the House of Commons Library have both noted the absence of a single overarching plan for adapting to extreme heat, and the committee's 2026 "Well-Adapted UK" report identified cooling and heat protection among the highest adaptation priorities. Friends of the Earth is calling on ministers to strengthen the National Adaptation Programme. The Commons Environmental Audit Committee has warned that heatwaves could claim up to 10,000 lives a year in the UK without concerted action, and costed heat-disrupted sleep at up to £60bn annually, or 1.5 to 2% of GDP.

Polanski also told the audience that parents cannot take children to playgrounds because slides are too hot, and that people are being kept indoors for days, turning cities into "ghost towns". He argued that Europe is warming at twice the global average rate.

Polanski was joined on the platform by a former soldier, a GP and a firefighter describing extreme-weather impacts in their work, alongside the broadcaster and naturalist Chris Packham. Packham used the event to call for a "transition to a plant-based diet", describing animal agriculture as a leading driver of biodiversity loss.

It was Polanski's first speech since he shared a post referencing the beheading of Reform UK leader Nigel Farage. He declined to apologise in a television interview, calling it an honest error. Reform UK referred him to the Metropolitan Police, which said it would take no further action. He did not mention the incident on Wednesday.

The attack carries an internal calculation. Polling suggests the Greens have dropped two points since Burnham entered No 10, while Labour has been first or joint-first in the last eight major polls with fieldwork since 24 July and Reform has fallen around three points. The Greens tripled their vote share to 40.6% in February's Gorton and Denton by-election, a 26.4-point swing from Labour, but Green candidate Geraldine Coggins took just 12% in the Greater Manchester mayoral election on 30 July.

Green MPs are split over how confrontational to be with a popular new prime minister, with some favouring restraint until Parliament returns and others pressing for attacks over defence spending and Gaza. The party had previously said it would "judge Andy Burnham on whether he provides the leadership necessary to deliver solutions". Green MP Hannah Spencer has tabled a bill to introduce a maximum workplace temperature.

Burnham, the country's seventh leader in a decade, became prime minister after Sir Keir Starmer announced his resignation on 22 June, citing a lack of confidence among MPs. Burnham was acclaimed Labour leader unopposed on 17 July with 379 nominations, more than 94% of the party's MPs, having returned to Parliament in the Makerfield by-election on 18 June with a majority of more than 9,000. In his first Downing Street address he described his appointment as a "circuit-breaker" and pledged a new political and economic model underpinned by a 10-year plan.

No government response to Polanski's claims had been issued at the time of publication.