David Cameron is facing a growing challenge to his authority from senior members of his own party who say they have doubts about the Conservatives' stance on global warming.
Leading figures including Peter Lilley, the former cabinet minister, Andrew Tyrie and Ann Widdecombe are openly questioning the political consensus on climate change.
And today David Davis, the former shadow Home Secretary, warns in The Independent that the policy of tough targets to cut carbon emissions, supported by Mr Cameron, is "destined to collapse". He criticises "the fixation of the green movement with setting ever tougher targets, in the face of failure to meet earlier promises". He adds: "The ferocious determination to impose hair-shirt policies on the public – taxes on holiday flights, or covering our beautiful countryside with wind turbines that look like props from War of the Worlds – is bound to cause a reaction in any democratic country."
Mr Davis is adamant that he is not a "denier" of climate change and accepts that it has "probably" been caused by human activity. But he is worried about the economic cost of meeting emissions targets. He wants other voices to be heard in the debate and a "middle way" found instead of the name-calling between "deniers and liars" on each side.
Mr Cameron has described the Copenhagen summit as "so important", saying: " What we need to see emerge from those discussions is an effective, binding and fair deal to cut carbon emissions that includes all major economies."
But Peter Lilley, who is tipped for a return to government if the Tories win power, told The Independent that while he believed the climate was changing the effects were being overstated.
"There is an irrefutable scientific process [on global warming]. I just think its effects tend to be exaggerated."
He added: "It is unrealistic to expect a satisfactory deal in Copenhagen. It is just not going to happen. The interests of the industrialising countries [such as China and India] differ so greatly from the already-industrialised countries."
Some Tory frontbenchers are also said to have private doubts about climate change. John Maples, the deputy Tory chairman, told the Commons last year that he no longer accepted the consensus on the issue. "I do not believe that the science is anything like as settled as the proponents of the [Climate Change] Bill are making out," he said. He declined to comment yesterday.
Backbenchers were happy to speak out. Philip Davies, Tory MP for Shipley, admitted he did not share Mr Cameron's views on the subject, and warned that a Tory government would harm the economy if it took unilateral action to cut emissions.
He said: "I would like to see some proper cost-benefit analysis [at Copenhagen] on the impact on the economy, rather than this charge towards trying to be trendy and to please the environmental lobby. Everyone has gone completely mad on this.
"It has taken on the hallmarks of a religion rather than a policy issue. Anyone who says 'hang on a minute' is completely decried and treated like a Holocaust denier," he said.
Graham Brady, Tory MP for Altringham and Sale West, said: "There is some room for debate about why the climate is changing and the best ways of tackling it. It is a good idea to reduce carbon emissions, but I would not want to see the whole economy destroyed in the process. There is a balance to be struck."
Mr Cameron led calls for a Climate Change Bill to entrench an emissions cut into law. But five Tory MPs voted against the measure last year – Mr Lilley, Philip Davies, Andrew Tyrie, Ann Widdecombe and Christopher Chope. Only about 40 of the 193 Tory MPs actively supported, and many abstained. Party managers were accused of imposing a low priority one-line whip to prevent a backbench rebellion that would have highlighted Tory divisions.
In the European Parliament last week, two Tory MEPs, Daniel Hannan and Roger Helmer, voted against a motion calling for the Copenhagen talks to agree an 80 per cent cut in emissions by 2050 – the official Tory policy.
They were among 18 members of the breakaway European Conservatives and Reformists Group, including its Polish leader Michal Kaminski, to oppose such a deal.
Last month Mr Helmer accused the Church of England of having "abandoned religious faith entirely and taken up the new religion of climate change alarmism instead".
Greg Clark, the shadow Energy and Climate Change Secretary, denied that the Tories were split, insisted the party's sceptics held "a minority view", and saw no evidence that their numbers were growing. "On policy, there is an increasingly strong consensus on what needs to be done," he said.
Cameron aides denied that the Tory leader would have to water down his strong personal commitment to green issues, saying that would drive the party's policy. They said all parties had climate change sceptics in their ranks.
Yesterday Lord Stern, a climate change economist, criticised the "muddled and unscientific" views of the sceptics in the face of what he described as "overwhelming" evidence.