The Carbon Trust is launching a green equivalent to the Fairtrade label - a consumer label which details the carbon footprint of a product and a commitment by its producer to reduce it.

Several major brand products, including Walkers crisps (carbon footprint: 75g), Boots Organics shampoo (148g) and Innocent smoothies (294g), will test the use of the logo - a white arrow wrapped in a black letter C. Over time it is expected that many more will join, raising the prospect that products might be marketed on the basis that they have the lowest carbon footprint in their marketplace.

The first product to be stamped with the logo will be Walkers cheese and onion crisps - the company's best-selling flavour. The Carbon Trust has enabled the company to identify the footprint of the three competing products in its range - crisps, Quavers and Doritos - by tracing its production cycle from the potato and corn producers at the start to recycling consultants at the end.

As a result, Walkers has reduced the carbon footprint of the product by a third. The trust established that farmers were hydrating potatoes to make them weigh more, because they were being paid a price per ton. Potatoes were stored in artificially humidified sheds to increase their water content. Humidifiers use large amounts of energy and generate significant emissions.

Walkers was then frying the sliced potatoes to remove the moisture. This increased overall frying time and fryer emissions by up to 10 per cent.

By changing the way potatoes are traded, the trust found that the Walkers supply chain could save up to 9,200 tons of carbon dioxide emissions and £1.2m a year. It recommended farmers be rewarded for producing potatoes with low water content.

Research undertaken by the trust shows that 66 per cent of consumers say they want to know the carbon footprint of the products they buy.

For products to carry the label, companies will need to have completed a rigorous analysis of their product supply chains, and commit to reducing the carbon level of their product over the next two years.