A guidebook unveiled in Copenhagen overnight makes mincemeat of the concept of "food miles", telling British shoppers that if they are really worried about their carbon footprints they could do more good by cycling or walking to the supermarket.

The advice by Oxfam and the International Institute for Environment and Development to avoid "knee-jerk" guilt about food miles will be music to the ears of New Zealand food exporters, who have long argued that the concept is simplistic.

The booklet's authors warn that misguided guilt about the distance food travels from paddock to plate could do more harm than good by destroying African livelihoods without significantly reducing greenhouse gases.

They quote studies showing transport accounts for 10 per cent of gas emissions in the British and American food chains.

The rest comes from food production, processing, distribution and storage.

They said produce grown in Africa under the sun and flown to Europe could produce fewer emissions than produce grown in Europe in heated glasshouses and carried by train or boat.

Many New Zealand food exporters are working to cut the carbon emissions of their products but they can do little about their distance to Europe. They believe New Zealand is being hurt by "buy local" campaigns that do not take into account the full carbon footprint of a product.

The booklet, out today, says the trade in fresh produce is vital to help rural African farmers prepare for the potentially devastating effects of climate change by strengthening their local economies.

The authors said farmers in developing nations contributed little to climate change, so it was unfair to penalise them for food miles.

They had another idea for shoppers who were serious about changing their behaviour to reduce greenhouse-gas emissions: cycle or walk to the supermarket.

The booklet also contains some advice that may be less palatable to New Zealand farmers.

It says that as meat and milk are leading sources of food-production emissions, shoppers should consider reducing the amount of them they buy.

But worldwide, meat and milk production is expected to double by 2050, leaving plenty of room to expand the market.

The guidelines come on the final day of the first of two weeks of intense negotiations on a climate treaty.

Officials have made some progress on the background rules, but observers in Copenhagen say the real breakthroughs are likely to come when ministers arrive to start trading numbers on Tuesday.

The first week was marked by strong words from Tuvalu, which with other island and low-lying states wants binding targets by rich countries to limit global warming to 1.5C - requiring greenhouse gases to be quickly stabilised at levels much lower than those of today.

Most developed countries want a 2C limit, and early signs are that negotiators will find it difficult to settle a treaty that achieves even the more generous target.