• See more Daily Mail on Google - save us as a Preferred Source

Green Party leader Zack Polanski today claimed the 'climate crisis' is the biggest threat to Britain since the Second World War.

The self-described 'eco-populist' said he was 'sounding the alarm' in the wake of the country's recent heatwaves, as he demanded urgent action from the Prime Minister.

Mr Polanski delivered his 'reality check' on 'extreme weather' at a press conference in Westminster, as he looked to bounce back from a series of scandals.

The Green leader has seen his personal ratings plummet in recent weeks, while his party were soundly beaten in last week's election for Greater Manchester mayor.

Despite a surge in support when Mr Polanski first became leader, the Greens have since fallen away in opinion polls.

The party has suffered a number of anti-Semitism rows, while Mr Polanski has faced questions over his council tax arrangements and his use of social media.

But Mr Polanski denied his stark warning about this summer's weather was a bid to stem internal criticism that he doesn't spend enough time talking about the environment.

He appeared at the Westminster event alongside BBC presenter Chris Packham, who said he 'fantasises' about climate change denial being made a criminal offence.

Green Party leader Zack Polanski claimed the 'climate crisis' is the biggest threat to Britain since the Second World War

Speaking at the same Westminster event, BBC presenter Chris Packham said he 'fantasises' about climate change denial being made a criminal offence

'Today I'm delivering a reality check, we are facing the biggest threat to this country since the Second World War,' Mr Polanski said.

The Green leader condemned Andy Burnham for not calling an emergency Cobra meeting in response to wildfires across Britain.

He demanded the PM introduce free 'cool spaces' in every local area, financial support for people to heatproof their homes, a new wildfire prevention strategy, and the nationalisation of water companies.

Fossil fuel companies should be made to pay for the cost of wildfires - such as funding firefighting helicopters - and extreme weather events, Mr Polanski added.

Several wildfires have broken out in the UK over recent weeks, with large blazes at Dunwich Heath in Suffolk, Llanwonno in the Rhondda Valleys, South Wales, and the Cairngorms National Park in Scotland.

Mr Polanski said, since the blazes, ministers had produced 'no emergency briefings, no new plan and precious little detail about how this Government will protect people from the crisis'.

He warned that 'the sheer scale of the devastation is hard to comprehend' but added: 'We need to look it in the face because this is only a taster of what's to come if we don't act now.'

The Green leader also urged Mr Burnham to 'be truthful, be brave' and block new drilling for oil and gas in the North Sea, including in the Jackdaw and Rosebank fields off the Scottish coast.

'Now, some will say we can't afford to make these changes,' he added. 'These last few weeks are showing we can't afford not to – we are facing an existential threat.'

Speaking at the same event, Mr Packham - the presenter of BBC Springwatch - said: 'To the disappointment of many, football didn't come home this summer. But to the pain and suffering of millions, climate breakdown has.

'Our Government and media response has displayed a total dereliction of duty in a time of extreme crisis.'

The broadcaster and naturalist, who has previously defended the actions of the Just Stop Oil group as the 'radical flank' of climate demonstrations, added: 'We've got to address the mis- and disinformation and we've got to do that with positive information campaigns.

'We've got to have people's minds on the front foot so they know what's true before they hear the lies. Then they will question the lies.

'Otherwise, you know what happens if you tell a lie frequently enough? It eventually becomes the truth. And that's what we're suffering from.

'We can't afford Net Zero'? We can't not afford Net Zero, and we're beginning to see that that's the case. We've got to sort out the media.

'I've been fantasising this year that we could perhaps criminalise climate denial - we should certainly criminalise irresponsible journalism.'

Mr Packham also called for a 'transition to a plant-based diet', warning animal agriculture was a 'leading driver of biodiversity loss'.