Another labelling war looks a step closer after Tesco signalled it would not be adopting the Carbon Trust's new carbon footprint labelling scheme as it stands.

As the Trust's label appeared on Walkers cheese and onion crisps for the first time this week, Tesco chief executive Sir Terry Leahy said the retailer would be using a different method to measure the carbon footprint of a product.

"We have noted what the Carbon Trust has done and it's a slightly different scheme than we propose," Sir Terry told The Grocer.

While the Trust measures a product's carbon footprint from "source to store", Sir Terry said this did not go far enough and consumption would also have to be taken into account.

He also claimed that a low-energy light bulb would not be distinguished from a standard bulb under the Trust's scheme.

His comments have sparked concerns that two different carbon labelling schemes could emerge, creating a divide like the one seen in the industry over front-of-pack nutrition labelling - and a headache for suppliers forced to measure their carbon footprint in different ways for different customers.

"This is absolutely our worst fear," said one leading supplier. "It would be of enormous concern if we went down two different routes. We will be adopting the Carbon Trust scheme and are working with them, but if Tesco comes up with its own label we will have to go with that, too. All this costs a huge amount of money for manufacturers."

There was also concern consumers might receive conflicting information, he said. "It's absolutely crucial to the consumer that we don't go off in two directions. It was too early to introduce the mark. Even the Trust has said that there is still a lot of work to do before it can come up with definitive standards. Both Tesco and the Carbon Trust have jumped the gun."

A Trust spokeswoman said a technical advisory group had been established to refine the methodology behind its mark and consult with academia, business, government, as well as environmental and consumer groups.

In spite of his apparent rejection of the Trust's trial label, Sir Terry said Tesco would continue to work with it on carbon footprint labelling. "This goes beyond the cut and thrust of business," he added. "We've had a very favourable reaction from other retailers and it's the most remarkable commitment we have made in terms of impact around the world."

"Tesco are supportive of the work we are doing," a spokeswoman for the Trust added. "We do not have all the answers yet but are working with our partners and other important stakeholders to get this right.Developing one standard credible way of measuring a product's carbon content that is universally accepted is essential and it will be important we all work together to achieve this."

Tesco stressed that it took the view that developing just one label was important. It also announced it would reduce the amount of packaging on both branded and own-label products by 25% by 2010 and would label all packaging according to whether it could be reused, recycled or composted, or none of the above.