Demand is mounting for a standard scientifically rigorous environmental labelling scheme that covers issues such as carbon emissions and water usage.
However, some retailers are worried that research underway on which such a scheme might be based may upset consumers by proving that some food sources are not as green as they have been led to believe.
According to one retailer, the research will show that some locally supplied fruit and free-range chicken is less sustainable than that sourced from overseas, or using more intensive production.
While UK retailers have taken the lead on carbon labelling, National Farmers' Union president Peter Kendall recently accused them of using different forms of carbon labelling to gain a competitive advantage. Speaking at an IGD think tank convention last month, Kendall called for a single agreed labelling scheme.
Chairing a round table on sustainability organised by Food Manufacture in October, Andrew Kuyk, director of sustainability and competitiveness at the Food and Drink Federation, said: "There needs to be a more authoritative source of information about carbon footprints." The round table was sponsored by Eversheds, British Gas and pump manufacturer Seepex.
Some experts believe that, rather than confusing consumers with different labelling schemes, retailers should 'choice edit' the most environmentally friendly products. "Can retailers do that on behalf of society?" asked Kuyk.
The alternative is to come up with a single scheme, which allows consumers to decide for themselves. But that is a hugely complex task, remarked Kuyk.
"Just as meat or dairy products are high in saturated fats, they are also probably going to be relatively high in carbon," he said. "Can a consumer actually understand a number and what does it mean? If we went down a 'traffic light' route for carbon labelling with foods, would people just try to fill their baskets with green, and would that mean they wouldn't get a balanced diet?"