Zack Polanski has accused Labour of a “dereliction of duty” in the face of this summer’s heatwaves, as he urged Andy Burnham to take further action in response to recent wildfires and droughts.

In a speech, the Green Party leader said the threat to public health and food supplies posed the “biggest threat to this country since the Second World War”.

Record temperatures in recent months showed the need for immediate measures, he said, such as publicly accessible “cool spaces” and financial support to help households heatproof their homes.

But Labour criticised the Greens’ record on reservoirs and clean energy projects, accusing them of “repeatedly” opposing new developments.

This summer has been exceptionally dry and hot, with temperatures setting numerous records and drought conditions leaving water supplies under strain and prompting warnings from farmers about the impact on food supplies.

Speaking in central London, Polanksi said higher temperatures were posing a “threat to our way of life” on multiple fronts, whilst footage of wildfires across Europe were “frankly apocalyptic”.

He called on Burnham, who entered Downing Street two weeks ago, to show greater urgency in response to high temperatures, as he criticised him for not holding an emergency government Cobra meeting on the issue.

“Extreme weather is now the new normal – and without action, the impact on the people of this country will be unimaginably grave,” he said.

The leader of the Green Party of England and Wales added: “The response from our government is to pretend none of this is happening.

“It’s an astonishing dereliction of duty from those whose first responsibility is to keep us safe”.

Among the immediate measures suggested by Polanksi were freely accessible cool spaces in “every local area”. He has previously cited a need for such zones in schools, hospitals and care homes.

Polanksi also renewed his call for Burnham’s government to block new oil and gas drilling licences, and block the development of the Rosebank and Jackdaw oil and gas fields in Scotland.

He also called for a new strategy to prevent wildfires following a series of blazes in various areas this summer, including “firefighting helicopters where needed”.

And he argued that the need to prevent future droughts justified his party’s longstanding policy of taking the water sector in England back into public ownership, arguing it would increase investment in new reservoirs.

However, Labour said the Greens had “repeatedly opposed plans for new reservoirs and clean energy projects” at a local level, which “makes it harder to achieve what they say they want”.

The party cited previous calls from Green councillors for a public inquiry into a planned mega-reservoir in Oxfordshire, and objections from local Greens to the size of solar farms planned in Norfolk.

“If Zack Polanski wants to tackle the climate crisis, he should start by telling his fellow Green Party politicians that actions speak louder than words,” a Labour spokesperson added.

“The Labour government will crack on with delivering these vital upgrades. The Greens should get on board.”

Burnham has said he wants all parts of the UK to take “greater public control” of the water sector, although he has stopped short of calling for all water companies in England to be fully renationalised.

He has suggested a new model for the sector could emulate Greater Manchester’s bus network, where private operators bid to run services on a franchise basis, with local authorities controlling fares, timetables and routes.

However, he is yet to spell out what an equivalent model for water would mean in practice.