It's not often Tesco is beaten at its own game, but its plan to launch a carbon footprint label was trumped last month by a packet of cheese and onion crisps. Walkers crisps will become the first product to carry the new Carbon Trust label, which shows the amount of greenhouse gases created in making a product and bringing it to shelf.

Alliance Boots and Innocent Drinks have also signed up - Boots is putting the label on shelf barkers while Innocent is carrying it on its website - and at least seven more are set to come on board this year.

But will the labelling scheme really help achieve the government's target of a 60% reduction on 1990 carbon dioxide levels by 2050? And is it in companies' interests to sign up to the scheme this early on?

Whether motivated by corporate concern or just a desire to pre-empt legislation, the early adopters of the Carbon Trust labelling scheme certainly feel the time is right. And there are plenty of financial incentives. The joint work between the Trust and Alliance Boots rationalised delivery and distribution by one third, hacking £1.4m off expenditure and producing an estimated annual reduction of 44,000 tonnes of CO2 emissions.

"Carbon equals cost," says group head of corporate responsibility Richard Ellis. "The finance and marketing men are happy and we can promote ourselves as socially conscious."

Better still, consumers are on side. Euan Murray, the Trust's carbon reduction label project manager, adds: "Companies have seen an increasing demand from consumers to communicate to them what is being done about footprint reduction. They want to inform consumers, shareholders and employees about what's been achieved."

The aim is to create a market-driven, carbon-conscious economy. But questions remain over the label's real worth. "We are concerned this approach is over-simplistic, as many different assumptions will have to be made in order to generate figures," says a Friends of the Earth spokesman. "The carbon footprint approach ignores other important environmental and ethical impacts of production."

Innocent admits its carbon footprint figures are not perfect and PepsiCo will modify its scores as new information comes to light. However, a calculated score is better than nothing, says Jess Sansom, sustainability manager at Innocent. "We must remember the object of the exercise: to cut and continue cutting emissions and empower consumers to make their own choices."

Others in full support of the scheme also stress the complexities of calculating a carbon footprint and communicating what it means. This is one reason why Sainsbury's is not rushing into carbon labelling and why Tesco will continue its own independent research alongside its work with the Trust to come up with its own labelling scheme.

"It's not an either/or situation," says a Tesco spokesman. "The label isn't the finished article and what's important is that consumers understand the meaning behind figures on a label. There are competing ideas about how best to do this."

Innocent is using its website to explain to consumers what carbon footprinting means. Its website says: "It's hard to put these figures into context but we can tell you that if you turn out the lights when you are not in the room each day, then you will negate the carbon impact of drinking one and a half smoothies per day."

Walkers is also using its website, although CEO Neil Campbell believes it is more important to get the label directly on the packaging. "It's the best way to reach millions of customers, even if they don't immediately understand all the implications," he says. "The label shows a commitment to carbon issues."

However, the fact that three different approaches have been launched within such a short period, albeit under the Carbon Trust banner (see panel) means that the label could be viewed as an endorsement rather than a piece of information, says Mallen Baker, development director of Business in the Community.

And let's not forget, carbon footprints on products are far from straightforward: it took Alliance Boots three months to confirm the footprint of just one Botanics product and there are 200 in this range. There are other issues. The label does not state that companies signed up to the scheme are committed to reducing their footprint or risk losing accreditation. It is a vital plank the Trust's £12m advertising budget will have to deal with.

The Trust acknowledges these issues. The current scheme is expected to undergo a year-long trial before being reviewed by its Technical Advisory Group, followed by widespread stakeholder consultation. "We do not have all the answers yet," says chief executive Tom Delay. "But there is a great deal of time and money being spent on finding them." n