"Food miles by road are far more important than we had thought. In environmental cost terms, buying local is even more important than buying green -- although we would like people to do both," Professor Jules Pretty of Essex University said.

In a groundbreaking study of food distribution patterns and hidden costs, Pretty and co-researcher Tim Lang of London's City University said food in Britain now travelled 65 percent further by road than it did two decades ago due to centralised storage.

Added to the fact that local shops were closing and being replaced by huge hypermarkets that meant people more often than not drove to get their shopping, this was taking a huge toll on the environment.

Cycling to the shops or even shopping online was better than the current unsustainable system, Pretty said.

Vehicle exhaust emissions along with the widespread use of fossil fuels like oil and coal to generate electricity are blamed by environmental scientists for producing greenhouse gasses like carbon dioxide and choking the atmosphere.

The scientists warn that global warming will push average temperatures up by at least two degrees centigrade this century, melting ice caps and leading to extreme weather events like floods and droughts, putting millions of people at risk.

Lang, who said he had coined the term 'food miles', said that while the study focussed exclusively on Britain it had relevance to the rest of the world.

"This is a global issue. It cannot be resolved by Britain alone," he told a news conference. "This is the first study of its kind. The figures are shocking. Other countries need to follow it up. The European Union needs to tackle this now."

Pretty noted what he called food swaps in which large quantities of apparently similar foods like milk and meat were both imported and exported by the same country.

One the face of it this did not seem to make economic sense and certainly did not make environmental sense, he said.

At the same time, centralised distribution networks in the developed world often meant that even staple foods like potatoes and beans travelled hundreds of miles to main depots only to be packaged and sent straight back.