Gordon Brown's leadership on environmental issues is flawed, according to Tony Juniper, who is stepping down as director of Friends of the Earth (FoE).
On issues such as climate change, the Prime Minister says one thing and does another, said Mr Juniper, who is leaving the green group after five years at the helm. During that time he has led a string of campaigns to success – notably "The Big Ask" campaign for mandatory reductions in Britain's greenhouse gas emissions, a concept now about to become law in the Climate Change Bill.
"Gordon Brown has talked a talk good on the climate-change issue in particular, but his policies are not matching the speeches," Mr Juniper said yesterday. "In November, one day he was talking about the need to cut emissions by 80 per cent, and a few days later he was out there at the front of the pack making the case for a third runway at Heathrow, which would generate emissions equivalent to the whole of Kenya.
"He hasn't joined up the dots – he's going in two directions simultaneously. Until he sees that the fundamentals of policy have got to reflect his overarching global concern, he isn't going to get very far."
An 18-year veteran of FoE, Mr Juniper, 47, was formerly a professional ornithologist, working for the International Council for Bird Preservation (now BirdLife International), where he was the in-house expert on parrots. Now, by common consent, he is the most effective of all Britain's eco-warriors. Although he will stay in the environment movement, he has decided to look for a change.
Many of the issues FoE has worked on in Mr Juniper's time have borne fruit, such as recycling (now compulsory for all local councils) and GM crops (turned down for commercial growth in Britain). But what gives him more pleasure than anything else is the shift in public perception about climate change in the past two years.
"We've gone through the most incredible transition," he said. "A couple of years ago it was, maybe it was happening, maybe it wasn't. But now the question has moved on. It's in the mainstream, it's become a public and political priority."
The Conservative Party leader, David Cameron, is partly responsible for that, Mr Juniper said: "The question is whether this has just been a rebranding exercise for the Conservatives, or a sincere environment agenda that's going to come into government with him, should he ever get there."
Mr Juniper also criticised celebrities such as Sienna Miller and Naomi Campbell who have endorsed green causes but who have talked the talk rather better than they have walked the walk.
Miller has admitted she would continue to fly but would take fewer baths, while Campbell came under fire from animal rights activists for appearing in real fur just months after endorsing a campaign to ban the use of fur in fashion.
"I'm not criticising people for their motivation, but celebrity endorsement needs to be properly integrated with political campaigns," said Mr Juniper.
An activist's life
* 1960: Born on 24 September to a worker at British Leyland and a waitress in Oxford. Grows up in a council house.
* 1980s: Studies psychology and zoology at Bristol University, then an MSc in nature conservation at University College London.
* 1990: Travels to Brazil and finds the last surviving Spix's macaw birds. In October, he joins Friends of the Earth.
* 1996: Takes over FoE's campaign on transport, GM food and world trade.
* 2002: Leads a slow handclap for the then US Secretary of State, Colin Powell, at the Earth Summit in Johannesburg as US refuses to sign the Kyoto Protocol.
* 2003: Detained at gunpoint by Swiss police after trying to gatecrash the World Economic Forum in Davos.
* 2007: Draft Climate Change Bill introduced in Parliament. FoE widely credited for influencing its contents.