Britain could go back to rationing

Mr Bradshaw pointed out that food production did just as much damage as private transport and housing.

He spoke out as a new government website advised shoppers to help the planet by avoiding meat, cheese and even British veg grown out of season.

The www.direct.gov.uk/greenerfood website makes clear that eating beef, lamb, chicken and dairy products contributes to global warming because of the energy and land needed to rear animals. Sheep and cows also emit harmful methane gas.

Mr Bradshaw told a meeting of food experts that the public would not currently tolerate a "nanny state" approach to what they ate. But he warned: "If the impacts of climate change are as bad as predicted, we may need to go back to rationing."

The website says that meat and cheese are among the worst for warming the planet, "because of the way they are produced, packaged, transported or cooked". Although transport and housing get all the blame for heating up the planet, food production and preparation do just as much damage, accounting for 25 per cent of global warming. Flying accounts for just two per cent.

Mr Bradshaw said the Government was considering a labelling scheme for all food products, based on the "farm to fork" impact each item has on the environment.

Mr Bradshaw also warned that green groups should not use "food miles" — the distance a product has travelled to get from farm to plate — to avoid products flown in from the world's poorest countries. He hit out at last week's move by the Soil Association to bar all air-freighted foods from getting its organic certificates.

"The public want to do their bit to help the environment but there are so many confused and confusing messages, particularly on the issue of food miles," he said.

"Flying in food from abroad accounts for a tiny proportion of the overall carbon emissions of the food industry, around three per cent. But around 13 per cent of emissions come from motorists travelling to and from the shops to buy food.