Only government intervention, meanwhile, would spur other British industries into moves such as cutting carbon emissions, which are blamed for global warming, they added.

In a keynote speech last week, Tesco chief executive Terry Leahy said the supermarket chain would spend 500 million pounds (762 million euros, 986 million dollars) on energy efficiency by 2012.

Leahy, addressing the environmental charity Forum for the Future, said Tesco had to take a lead among British business in tackling climate change.

"As a growing international business, we must set an example by measuring and reducing our greenhouse gas emissions.

"By setting targets that stretch our business and by committing to do this in public, we are transparent and fully accountable for what we achieve."

Leahy promised independently-audited cuts in carbon emissions from its operations, support for the development of emerging low-carbon technologies and carbon labelling on all of its products.

Forum for the Future hailed the announcements.

"Tesco's commitment to count and display the carbon cost of every product is groundbreaking," the group's chief executive Peter Madden said.

"It shows that they are serious about tackling climate change and intend to do it by helping millions of customers make straightforward and affordable choices."

Tesco's move meanwhile came in the same week that Marks and Spencer announced plans to spend 200 million pounds over the next five years on its own eco-plan.

"Every business and individual needs to do their bit to tackle the enormous challenges of climate change and waste," M and S chief executive Stuart Rose said.

The food retailer, which also sells clothes made from organic cotton, said its plans included moves to make Marks and Spencer 25 percent more energy efficient, in part by creating renewable energy generated from its own waste.

It added that it would "minimise" the amount of food it transports on planes, while ensuring that its key raw materials come from "the most sustainable source possible, in order to protect the environment and the world's natural resources".

Friends of the Earth Director Tony Juniper praised the moves, claiming that M and S was taking a lead among British business in cutting its waste and carbon emissions. But he added: "The government also has a role to play in giving business (elsewhere) the confidence to take similar action. They can do this by delivering a strong climate change law which commits the UK to making annual reductions in the UK's carbon emissions." Britain's finance minister Gordon Brown, the man tipped to replace Tony Blair as prime minister later this year, revealed recently that he was taking steps to limit his own carbon emissions, such as by driving a smaller car.

Should Brown become prime minister, it remains to be seen whether his government will introduce stricter green policies that would ensure other British retailers mirror the efforts being made by Tesco and M and S.

"If every retailer in Britain followed Marks and Spencer's lead it would be a major step forward in meeting the challenge of creating a sustainable society," said Blake Lee-Harwood, campaign director for Greenpeace UK.

Tesco meanwhile claimed in December that it had opened the country's "greenest supermarket", in Wick, Scotland -- pointing for example to the use of wind turbines to power its checkouts. However Sandra Bell, supermarkets spokeswoman for Friends of the Earth, dismissed Tesco's self-appointed tag.

"They are calling it the green supermarket but yet it is a huge store on the edge of a small town. So it's going to be drawing in shoppers in their cars over long distances," she argued. "Sticking wind turbines on the roof is a useful initiative but it doesn't mean Tesco can call itself an environmentally sustainable company."

Bell criticised Tesco and other British supermarkets, in particular for "constantly pushing prices down to their suppliers", which she said resulted in their being unable to invest in environmental measures.

"With overseas suppliers, it could mean that companies supplying supermarkets have to source from countries with lower environmental or ethical standards to meet the price that the supermarkets are demanding."

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