Ed Miliband has joined a cross-party attempt to persuade voters that leaving the EU would damage the environment.
The former Labour leader has signed a joint declaration with environment secretary Liz Truss, former energy secretary Ed Davey and Green Party MP Caroline Lucas in what pro-EU campaigners called an unprecedented partnership.
They claim that those campaigning for Brexit are climate change deniers who are ignorant of the potential impact.
“Collective action is the only solution to rising seas and rising temperatures. The European Union is central to both these challenges,” they say in a pamphlet setting out the arguments.
EU membership supported domestic action to improve air quality, protect nature and wildlife and invest in renewable energy, they say, and Brussels is “a leader in the battle to secure binding agreements” internationally.
“Those campaigning for Britain to leave Europe cannot be trusted on the environment,” they say.
“They have opposed vital green measures and denounced climate change as ‘mumbo jumbo’. They demonstrate a cavalier ignorance about climate matters which embodies the extreme and out-dated outlook of those who want to leave.
“If Britain leaves Europe, our environment, our wildlife and our global habitat will be starved of investment, bereft of protections and denied the leadership it needs,” the declaration says.
But environment minister George Eustice – who supports Vote Leave – said the EU had “systematically undermined the UK’s place on international wildlife conventions”.
“We have already been stripped of our voting rights on regional fisheries management organisations and, extraordinarily, it is now unlawful for the UK to speak at wildlife conventions like Cites (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) without first getting permission for what we want to say from the European commission.
“If we vote to leave and take control, the UK would regain its own seat and its voice in vital international wildlife conventions and everything from promoting shark conservation to ending whaling would become much easier.”
In a further development, Tory grandee Michael Heseltine has criticised MPs backing Brexit for turning on the government during the debate. The former cabinet minister said some Tory MPs owe their jobs and the party’s surprise general election victory to David Cameron.
He told Sky News: “The facts are that he won this election for the Conservatives, and now to see people who, frankly, many of them would not have their seats and certainly many of them wouldn’t be in government if David Cameron hadn’t won that election for the Conservatives.
“And to see them now turning on the policies that some of them have been sitting in the government implementing, I just find mind-blowing.”
It comes after senior figures insisted the Conservatives could unify after what has been a fractious EU referendum campaign. On the Andrew Marr show, Ukip leader Nigel Farage claimed Cameron would not continue as prime minister if the UK voted to leave the EU.