Tesco has today launched an impassioned defence of its plans to put carbon labels on all its products, rejecting accusations that the labels confuse customers and insisting that its pilot scheme has already delivered significant tangible benefits.

Speaking as part of a panel discussion at today's Corporate Climate Response conference in London, Philip Cullum, acting chief executive of the National Consumer Council argued that the practice of putting carbon data on products, as currently being trialled by Tesco, Walkers Crisp, Innocent Smoothies and Boots as part of a Carbon Trust orchestrated project, is confusing customers.

He cited research from the Carbon Trust which claimed that while customers welcomed having environmental information on products a large majority admitted to not knowing what the carbon footprint figure meant. He added that the practice of communicating carbon data to customers was a "side issue" in relation to retailers' broader efforts to curb carbon emissions.

However, in a tense exchange Tesco's director of government affairs and corporate responsibility David North launched a fervent defence of the policy, challenging Cullum to identify exactly what it was he felt was confusing about the carbon labels currently being carried by 20 Tesco products.

Quoting William Tyndale, the 15th Century scholar who first translated the bible from Latin into English and was martyred for the privilege, North argued that it was invariably in the social interest to support the dissemination of information and challenge those elites that "keep the world still in darkness, to the intent they might sit in the consciences of the people".

Dr Steve John, corporate affairs director at Walkers' parent company PepsiCo, downplayed concerns over customer confusion, arguing that understanding of carbon labelling would evolve over time. "It's true that consumer understanding of the figure was not high, but that is exactly where you'd expect it to be at the start of the story," he said. "Also all our quantitative and qualitative research showed that while they may still be unfamiliar with the figures customers welcomed the information being there."

Supporters of the scheme also insisted that the practice had already delivered tangible benefits. North said that it was too early in the trial to report on the impact on sales, but he admitted that the results looked "pretty encouraging so far". He added that the process had also delivered data that could help shape consumer decisions, revealing, for example, that concentrated washing liquids have a lower footprint than powders.

He further argued that the practice of measuring carbon emissions had allowed the company to identify a number of areas where it could deliver improvements in the carbon efficiency of its supply chain. "The process allowed us to identify hot spots within the supply chain," he said. "For example, we were able to uncover one supplier whose refrigeration units were far less efficient than those of a rival and were therefore able to work with them to rectify that."

John agreed that the practice of measuring a product's footprint combined with the public commitment to ensure that the figure falls over the next two years had already impacted on the firm's supply chain. "Every capital expenditure and business decision is now looked at through the lens of the push to reduce CO2 over the next two years," he said, adding that carbon labels could potentially have a similar impact on food companies as nutrition labels – instigating an arms race between competitors to achieve best in class performance.

Moreover, the process has proved more cost effective and less time consuming than originally expected, according to North and John, with the standardised approach to carbon measurement developed alongside the Carbon Trust allowing firms to complete calculations within a matter of a few months. "We were told this would cost us £50,000 per product, but the cost is now down to £2,500 per product and falling," observed North.

However, Dr Brenda Boardman, senior research fellow at Oxford's Environmental Change Institute, argued that while the emergence of carbon labels was welcome there are numerous technical problems that need to be addressed if carbon labels are to prove effective at changing consumer behaviour.

She observed that there needed to be an agreement on where the boundaries for carbon footprint calculations are drawn, arguing that such measurements should not extend "beyond the shelf" and should only focus on areas the supplier can directly control. "I don't want companies telling me that if I wash my hair with cold water that will lower the shampoo's carbon footprint," she said.

She also argued that carbon labels will only prove truly effective when consumers can compare carbon footprints using an A-G colour rating system similar to that shown on electrical devices. However, she warned that the development of such an approach would only be possible if agreement is reached on how to categorise products. "We have to ask if all meat products will go into the G band, or if beef goes in the G band and chicken goes in a lower band, or if just the most carbon intensive beef goes in the G band with other beef products going elsewhere," she observed.

Firms also have to balance the advantages of carbon labels against the need for other labelling schemes, according to Richard Naylor, UK environment manager at drinks firm Scottish & Newcastle. He said that the company was unlikely to carry carbon labels on individual beer cans as it also had to make space for responsible drinking labels and did not want to overwhelm the customer with information.

However, Tesco's North insisted that carbon labels were already delivering numerous consumer and business benefits and confirmed that the company remained committed to its long term goal of carrying carbon labels on all its products. He also urged other firms to join the pilot scheme, arguing that it is only through collaboration that such initiatives can maximise their success.