He talked of his fears of the legacy that Prince William’s and Prince Harry’s children would inherit if action was not taken. “We should be treating the whole issue of climate change and global warming with a far greater degree of priority than is happening now,” he said in an interview at his Highgrove estate.

“If you think about your and my grandchildren, this is what really worries me. I don’t want them — if I’m still alive by then — to say, ‘Why didn’t you do something about it?’, when you could have done.

“At the same time as trying to do something to rectify the situation — which should be the greatest challenge to face man — we have to work out how we adapt to the changing situation . . . what crops to grow, for instance.”

The Prince was speaking at Home Farm, regarded as a model of organic agriculture. A large notice greets visitors: “Caution. You are entering a GMO-free zone.” There is not a rusty piece of farm machinery in sight on the 1,800 acres. All livestock are treated homeopathically and the estate has its own natural sewerage system with drains filtered through reed beds.

The Prince has taken delivery of a Toyota Prius hybrid car which is partly powered by electricity. His range of organic products, Duchy Originals, now grosses more than £1 million annual profit for charity. The dairy is solar powered and he is experimenting with wood chip boilers to heat Highgrove.

At a seminar at St James’s Palace this year he urged business leaders to adopt a public education programme on energy saving. He said: “I do go round clicking off switches. There is also no boiling a whole kettle when making a cup of tea.”

Yet the Prince, whose income last year from the Duchy of Cornwall was £14 million, is regarded by some royal courtiers as a lavish spender compared with the Queen. The heir to the throne is regularly criticised by MPs over the cost of his official travel, which doubled last year to £1 million.

He spent almost £300,000 chartering a plane to visit vicitms of the tsunami and will spend £200,000 on chartering a flight to the United States for his first official overseas visit with the Duchess of Cornwall. By contrast a trip by the Duke of Edinburgh to Toronto cost £12,800 on a scheduled flight. And besides the hybrid car, the Prince has eight other cars, including two Aston Martins and an armour-plated Bentley.

The Prince, who was speaking to BBC News 24, said he had always tried to grow things in the most natural possible way. “I felt it was inherently unsustainable to go on being able to expect endless chemicals and artificial fertilisers poured on (the land) and not suffer the consequences.”

He despaired at the advances in technology that had caused such huge changes to the countryside. “You can suck every last drop of the things that make life worth living out of it.”

The Prince also expressed his fears over the plight of poultry farmers who have been threatened by the emergence of avian flu. In 2001 he donated £500,000 to help farmers hit by the foot-and-mouth outbreak.

The Prince, who is president of the Poultry Club of Great Britain, said: “I feel so deeply for the . . . poor old poultry farmers in this country.” He praised the farmers who had resisted the financial temptation to put their chickens into intensive battery production. “They have struggled to get their chickens outside for all the right reasons. Then to find suddenly that they might have to shut them all up. It’s very worrying, but you can only, you just have to, pray.”

The Prince has a flock of almost 100 chickens on his farm with a handful at Highgrove. He said he still allows them to “potter outside”. The eggs from the farm are sold along with vegetables to about 200 houses nearby. Eggs from Highgrove are used at his own table.

Prince Charles described how, as a young boy, he and his sister, the Princess Royal, grew produce on a small vegetable patch at Buckingham Palace. He confessed he had “always wanted to do a bit of farming” and joked: “I’m not very good at it, but fortunately lots of other people were around to help.”

The Green Party applauded the Prince’s warning but added that, if he was serious about climate change, it would like to see “more use of the Royal Train when travelling in Britain and less flying”.

The Royal Train, used by the Queen, is one of the most expensive forms of travel at £49 a mile.

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