Without such a deal, scientists warn that world temperatures will increase by more than 2C by the end of the century, triggering ice cap melting, sea-level rises, widespread flooding, the spread of deserts and devastating storms.

In a speech in the parliament last week, Griffin denounced those who warn of the consequences of climate change as "cranks". He said they had reached "an Orwellian consensus" that was "based not on scientific agreement, but on bullying, censorship and fraudulent statistics".

"The anti-western intellectual cranks of the left suffered a collective breakdown when communism collapsed. Climate change is their new theology… But the heretics will have a voice in Copenhagen and the truth will out. Climate change is being used to impose an anti-human utopia as deadly as anything conceived by Stalin or Mao."

Griffin will be one of 15 representatives chosen to speak on behalf of the EU in Copenhagen. The shadow climate change secretary, Greg Clark, condemned the move last night. "It is utterly ridiculous that someone who doesn't even believe in climate change should be seeking to represent Europe in Copenhagen. The BNP does not command the support of the people of Britain, let alone of the rest of Europe," he said.

Tim Yeo, chairman of the Commons environmental audit committee, said the decision to choose Griffin showed the "bizarre way" the parliament operated. He added: "If the future prosperity of the human race, in the face of climate change, depends on the contributions of people like Nick Griffin, there is little hope for any of us."

Professor Alan Thorpe, chief executive of the Natural Environment Research Council, said Griffin's claim that thousands of scientists dispute the existence of man-made global warming was simply not true. "The intergovernmental panel on climate change draws on the views of most of the world's leading climate scientists and they have been quite clear that the evidence shows, with a high degree of certainty, that human activities are now having a substantial effect on the climate. It is simply not the case that there is a substantial number who do not accept a link."

Bob Ward, of Grantham Research Institute on Climate Change and the Environment, said: "Griffin denies the overwhelming scientific evidence on climate change. This appears to be driven by a dogmatic strand of right-wing ideology that opposes any form of environmental regulation, usually hidden behind the dishonest claim that climate change is a left-wing conspiracy."

Critics say Griffin addresses environmental issues when he believes he can use them to advance anti-immigration policies. His party claims that it would improve Britain's transport infrastructure and reduce carbon dioxide levels by reducing the number of immigrants in Britain using roads, cars, trains and buses.

But Climate Change Secretary Ed Miliband said Mr Griffin "cannot and does not represent the views of the people of the UK or of Europe.

"He will not be part of the formal Copenhagen negotiations and rightly he will not be listened to by anyone with any credibility who is part of these negotiations."

Shadow climate change secretary Greg Clark told Sky News it was "ridiculous" that Europe would be represented at Copenhagen by someone who questions the existence of climate change.

"It's a concern that Nick Griffin is representing the people of the European Union when he doesn't even represent the views of anything more than a tiny minority of Britons," he added.

"The idea that he speaks for the people of Europe is ludicrous."

Green Party leader Caroline Lucas also played down the impact that Mr Griffin's presence would have.

"He is one of a number of members of the European Parliament who will go on a delegation," the MEP told BBC1's Andrew Marr show.

"He won't get the right to speak. The Parliament sadly doesn't even get the right to really influence the decisions at all.

"So this idea that somehow Nick Griffin is going to have any real influence on what happens in Copenhagen is a myth."

Obviously with the Copenhagen Climate Summit a mere week away... the emergence of ANY evidence challenging the idea that current climate change is NOT a man made problem, would be, to say the least, unfortunate.

Sky weather presenter Jo Wheeler

It came as Mr Miliband said there was still work to be done to achieve "the most ambitious, comprehensive agreement we can" at the summit, which begins on December 7...

"We have come a long way but there is still a distance to travel to get the agreement we need, consistent with the demands of the science."