Genetically modified foods and nuclear power had, for years, provoked the ire of leading environmental campaigners who have now done a volte-face on these issues.
Opposing nuclear power meant encouraging use of polluting coal-fired power stations, while protesting against GM crops meant preventing developing countries from benefiting from a technology that could have helped feed the hungry, they have said.
Mark Lynas said the environmental lobby was losing the battle for public opinion on climate change because it had made too many apocalyptic prophecies and exaggerated claims.
"I would like to see an environmental movement that says it turns out our fears about genetically engineered food crops were exaggerated and we are glad about that. It is a humble and modest stance to take to the real world," The Telegraph quoted Stewart Brand, an American activist and former editor of Whole Earth Catalog, as saying.
Patrick Moore, one of the founding members of environmental campaign group Greenpeace said that they weren't against nuclear power "completely".
"We have caused extra gigatons of greenhouse gases to be released into the atmosphere by being so precious about nuclear," he said.
They say that by successfully lobbying against the building of new nuclear power stations, environmentalists forced governments around the world to build new coal fired power stations instead, resulting in billions of extra tonnes of carbon dioxide and pollution being poured into the atmosphere.
The activists feature in the Channel 4 documentary What the Green Movement Got Wrong, which will be broadcast this week.