There are very sensible reasons to have a healthy balanced diet, and I think some people eat too much meat, but I think there are other more useful things one can do to reduce one's carbon emissions."

The Indian expert's suggestion was also criticised by mayor of London Boris Johnson. "No, Dr Rajendra Pachauri, distinguished chairman of the panel, I am not going to have one meat-free day per week. No, I am not going to become a gradual vegetarian," he told London's Daily Telegraph. "In fact, the whole proposition is so irritating that I am almost minded to eat more meat in response."

Chris Lamb, head of marketing for pig industry group BPEX, said the meat industry had been unfairly targeted. "Climate change is a very young science and our view is there are a lot of simplistic solutions being proposed," he told the Observer.

The National Farmers Union said "simplistic measures" to reduce meat consumption would "create more problems than they solve". A spokeswoman said: "The NFU is committed to ensuring farming is part of the solution to climate change, rather than being part of the problem."

Stuart Roberts, director of the British Meat Processors Association, said he was "disappointed" by the comments. "The British meat industry already takes its environmental responsibilities very seriously and I believe methane levels on UK farms are actually falling already."

Britons in large numbers posted their comments on the internet editions of several British newspapers, a majority of them reacting in a critical vein. Britons eats a million tonnes of beef a year, 1.3 million tonnes of pork and 1.8 million tonnes of poultry.

An anonymous person posted on The Telegraph site: "First eat a steak, done the way you prefer it. Then after that has made its way through and out of your system, eat cabbages, beans, spinach, etc and compare the amount of methane produced between the two. The second result will rival the amount gushing out of the mouths of these 'experts'."

Here is another anonymous post: "What else would he say, the man's a vegetarian!"

Posts supporting Pachauri were noticeable too, though fewer than the critical ones. Here is an example: "I think it's very sad that a gentle, modest, rational call to help limit damage to the earth from someone in a developing country (India) meets with so many irrational comments from the UK public.

"It's in our own interest to eat more plant-based whole foods and less animal products, as meat and dairy are strongly linked to incidence of most of the major western diseases like heart disease, most cancers etc. And optimum development and health means eating much less animal products than the average UK diet."