Carbon labelling is dividing manufacturers and leaving consumers confused, according to environmental consultants and retailers.
Marks & Spencer (M&S) has cast doubt on Tesco's labelling plans, while the Soil Association (SA) has accused both retailers' labelling systems of "passing the buck to consumers"
Speaking at a carbon footprint convention organised by the Food and Drink Innovation Network, Alan Knight, founder of Single Planet Living, which advises firms on sustainable development, said: "I fear we haven't quite thought this through. Tesco is introducing carbon labelling on potatoes, but how consumers cook a potato makes much more difference to its environmental impact than the number on the product's label."
Rowland Hill, sustainability manager at M&S, agreed: "Only Tesco is taking up this particular approach. It did a lot of research [on carbon footprinting] and the labelling issue wouldn't have been what I'd have taken out of it."
Knight suggested companies would do better to use choice editing, where the retailer only sells products with a carbon footprint it deems satisfactory. "We are entering a perfect storm that, if we don't manage, the Daily Mail will," he warned.
Separately, Simon Aumonier from consultancy Environmental Resources Management, which worked with Tesco on its carbon footprinting research, claimed air-freighted labels used by M&S were confusing consumers. "Food miles are misleading and often have an insignificant effect on a product's carbon footprint. Air transport is not always bad."
Research shows that flowers flown from Africa can use less energy overall than those produced in heated greenhouses in Holland. "People don't understand that Dutch flowers have a higher carbon footprint," Aumonier said.
But Hill argued that M&S launched the air-freighted label because it wanted to prove it only flew in produce when UK foods were out of season. "Now people understand why we provide goods from different parts of the world."
The SA, which is to tighten organic certification of air-freighted produce, slammed both retailers' labelling schemes.
"Slapping an aeroplane on products and doing nothing else about it is the wrong route," said policy director Peter Melchett. "We're not just passing the buck to the consumer, which is what Tesco and M&S are doing."
From 2009, SA accredited air-freighted products must meet its Ethical Trading standard or the Fairtrade Foundation's standard.