Carbon footprint labelling will have an even greater impact on consumer purchasing than nutritional issues, according to Tesco director Lucy Neville-Rolfe.

"Green consumerism is set to be the biggest consumer trend of all," she said at IGD's Global Retailing Conference. Tesco was "determined to lead the green revolution", she added, but admitted: "We are faced with a mighty challenge to come up with a label that makes sense to consumers.

"The fact there can be less carbon involved in the production and transportation of a crop grown in Africa compared to Europe is nonsensical."