"In the past, retailers have responded in slightly different ways, sometimes in terms of doing what consumers want rather than what is the best option environmentally," said Hailes, who has advised chains from Marks & Spencer to Morrisons.

Different retailers have chosen to highlight lightweight packaging, compostability, the use of renewable resources, recycled content, recyclability and overall carbon footprint. Experts agree this is potentially confusing for consumers. The CC2 emphasis on carbon could provide a new, more unified focus, she said.

She criticised the idea, aired in the context of fresh milk in polybottles and pouches, that consumers should make their own assessments regarding the relative merits of packs. "It's even difficult for me, as an expert, to do that. The message has to be that the firm has done the research and assessment, and has made the decision for the consumer."