The television presenter and conservationist is the president of Plantlife International and of the Royal Society of Wildlife Trusts. Both organisations have given warnings that wildlife faces a catastrophe because of global warming.

They have been acutely embarrassed to discover that while they have been campaigning to raise awareness, their president has been leading seminars and writing articles in science magazines declaring that man-made warming is a myth.

Last week Plantlife International, Britain’s leading charity dedicated to the conservation of wild plants, wrote to Bellamy to say that his term of office would end in the autumn and he would not be asked to renew it.

His presidency of the Wildlife Trusts — which has 562,000 members and manages 2,500 nature reserves — also ends in the autumn and is unlikely to be renewed.

Stephanie Hilborne, chief executive of the Wildlife Trusts, confirmed that Bellamy’s position was due to be discussed at a board meeting at the end of this month.

“We are not happy with his line on climate change. It is a very serious situation and there is a lot we need to talk about,” she said. “Our views certainly differ from our president’s and that is not a good situation to be in.”

Both organisations paid tribute to Bellamy who, they said, had put a huge amount of time and effort into supporting their other work.

Bellamy, 72, a former botany lecturer at Durham University, endeared himself to generations of youngsters with a series of popular wildlife programmes that ran from the 1970s through to 1999. He has also written many wildlife books.

He won respect from hardline environmentalists with his campaigns to save Britain’s peat bogs and other endangered habitats. In Tasmania he was arrested when he tried to prevent loggers cutting down a rainforest.

In January he gave a keynote speech at the Royal Institution in London which was hosting Apocalypse No, a conference organised by the Scientific Alliance.

“Global warming is a largely natural phenomenon. The world is wasting stupendous amounts of money on trying to fix something that can’t be fixed,” he said.

Last month he made similar assertions in New Scientist magazine when he claimed that glaciers were expanding because the world was getting cooler rather than warmer. The claim contradicted recent scientific studies that found 85% of the world’s glaciers are in retreat.

Bellamy said this weekend: “If an organisation asked me to stand down of course I would, if they actually think I’m doing more harm than good.”

He added: “The climate-change people have no proof for their claims. They have computer models which do not prove anything. When I say that they say ‘You must be in the pay of the oil industry’. I’m not. I’m not in the pay of anybody.”

Additional reporting: Chris Whyatt

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