The validity of food miles as an indicator of sustainable development was a key theme at the Climate Change and the Food Industry conference in London last week.
Food miles cost the UK economy an estimated £9bn per year through factors such as congestion, noise and infrastructure damage, according to Paul Watkiss, co-author of a 2006 Defra report on the impact of food transport on the environment.
He argues that the concept of food miles is too simplistic and misleading.
"There is no reason that food produced in Kent is more environmentally friendly than that produced in Kenya," he says, adding that the phrase "food vehicle km" rather than "food miles" is a more accurate measurement.
Watkiss has recommended a set of indicators that have been accepted by Defra and are expected to be issued shortly. The indicators are: urban food vehicle km, HGV food vehicle km, air food vehicle km and Co2 emissions.
Maritime freight emissions, however, are very low and goods transported by sea "appear to be a fairly benign load - especially compared with air freight".
Asda's head of ethical and sustainable sourcing, Chris Brown, agrees that while food miles are important they are should not be the overriding concern for retailers or manufacturers trying to green the supply chain.