Boris Johnson should publicly declare climate deniers as wrong in order to secure the UK’s standing in vital UN climate talks this year, campaigners have urged, as climate deniers with links to the Tory party prepare for a new battle.

As the UK leaves the EU, and its emphatic environmental commitments including the European green deal, those who want to see less action on the climate crisis are hoping Johnson’s government will be more amenable to delaying and watering down green measures.

The EU on Wednesday sets out its first ever climate law, the long-awaited centrepiece of the European green deal, which is designed to prepare the EU economy for dealing with the climate emergency. The new law would enshrine a 2050 net zero emissions target in legislation and empower Brussels to take governments to court if they fail to comply. But the UK prime minister has yet to articulate a strategy for meeting Britain’s target of net zero by 2050, giving the advocates of delay and distraction everything to play for.

Climate denial is taking new forms, some experts say, moving from an outright rejection of science to covert attacks on green policies and spending on efforts to cut carbon. The EU’s green deal has prompted frantic lobbying in Brussels by powerful fossil fuel interests, as a Guardian collaboration with other European media organisations this week reveals.

But the Tory party retains links with prominent individuals who are climate deniers, or who are connected to organisations that either deny the climate crisis or actively work to undermine climate policies, such as the Global Warming Policy Foundation, the thinktank set up by the former Conservative chancellor Lord Lawson.

“The GWPF have shown themselves to be tremendous opportunists,” said Bob Ward, policy director at the Grantham Research Institute on climate change at the London School of Economics. Ward claims the thinktank has been fundraising heavily in the US – as well as spreading its views to ministers and across Whitehall – to raise money for a major campaign to influence the Johnson government.

“I expect that as the economy continues to take a hit from Brexit that the GWPF will attempt to mislead policymakers into believing the cause is climate policy.”

Sir Michael Hintze, a hedge fund billionaire who is a long-time major donor to the Tory party, is understood to be a funder of the GWPF, which is not required to disclose its funding, and is also understood to have provided support to Priti Patel, Dominic Raab and Andrea Leadsom, among other Tory MPs. Matt Hancock has accepted donations from Ian Taylor, the chairman of oil trader Vitol, while Michael Gove and Liz Truss have been linked to the the American Enterprise Institute, which lobbies political, business and public opinion against action on the climate crisis.

There is no suggestion of wrongdoing on the part of the Tory MPs. However, in the current climate crisis, experts have raised questions about the Tories accepting funds from individuals with fossil fuel interests or linked to climate denial organisations.

“Well-connected climate sceptics must be called out by ministers, from the prime minister down,” said Shaun Spiers, the executive director of the Green Alliance thinktank. “We have seen the damage that well-funded rightwing campaigns against climate action have done in the US, Australia and Brazil. Conservative environmentalism is stronger than ever, with the party officially recognising the seriousness of the climate emergency. It should disassociate itself from the deniers.”

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This year’s UN talks on the climate are the most important since the Paris agreement in 2015, as the world is now far adrift of the Paris goals. The Cop26 summit set for Glasgow in November is seen as a last chance to get back on track to avoid climate breakdown, but the UK will face an uphill struggle to bring other countries on board with strong new carbon-cutting commitments. That will not be helped by any perception that the Tory party is sympathetic to, or funded by, climate sceptics and deniers, and fossil fuel interests, experts told the Guardian.

Johnson should claim the mantle of Margaret Thatcher, advised Mohamed Adow, the director of developing country thinktank Power Shift Africa, and a longtime observer of the UN climate talks. “[Cop26] is an opportunity for Johnson to show that he’s broken with those dinosaurs of the past, and is instead showing that tackling climate change transcends tribal politics. His predecessor Margaret Thatcher was the first western leader to give a speech on climate change at the UN, so he won’t be the first Tory to show leadership on this issue,” he said.

Other countries would be watching closely, warned Adow: “It is a problem that the Conservatives are so closely linked to discredited organisations like the GWPF. If Britain is going to be taken seriously by the rest of the world, [the Conservative party] should distance itself from these shady groups who try to undermine efforts to address the climate crisis.”

As well as disavowal of denialist arguments, Johnson must set out clear measures to fulfil the UK’s own climate goals, added Alasdair Cameron of Friends of the Earth. “The voices of denial or delay are obviously scrabbling to stay relevant, but in truth are fading fast,” he said.

“However, it will not be enough for government to simply accept that there is a problem. The UK has the opportunity to be a leader in building a positive zero-carbon future, but it will require urgent and concerted action at home and abroad, and right across government.”

Doug Parr, the chief scientist at Greenpeace, said that although the government was espousing green policies, it was inconsistent. “Inside the Boris Johnson government, climate denial seems to have morphed into something else – a form of cognitive dissonance. It’s the contrast between acknowledging that there’s a climate emergency and keeping expanding fossil fuel exploration, funding oil and gas projects overseas, and spending billions on new roads. This way of thinking is ultimately on a collision course with reality.”

Johnson has made only one public appearance on Cop26 so far this year, attending the launch in front of a group of schoolchildren and more than 100 dignitaries. But the event was overshadowed by criticism of Johnson by Claire O’Neill, the former energy minister who was to be Cop26 president but was abruptly sacked a few days before.

She accused Johnson of a lack of knowledge and commitment on the climate crisis. She was replaced last month by Alok Sharma, the new business secretary. Some green campaigners are concerned that his dual role will create a conflict of interest and prevent him from standing up to vested interests reluctant to move urgently to a low-carbon economy.

Hintze said in a statement from his spokesman: “I believe that the increase in concentration of carbon dioxide is in part due to human activity over the past century and that it has been a cause of global warming. But the sole focus on CO2 is too narrow and there are many contributors that need to be considered. All sides must be heard to reach the right conclusion for society as a whole.”

Benny Peiser, the director of the GWPF, said the organisation was always fundraising, but did not disclose its donors. He said Cop26 was unlikely to make much progress: “The international community is deeply split on this and I do not expect anything more than a continuation of the deadlock.”

A Conservative party spokesperson said: “Tackling climate change is one of the Conservative party’s top priorities, and this government is working tirelessly day in, day out to achieve our ambitious targets.”