More than 150 companies round the world on Thursday pledged to reduce their carbon emissions voluntarily and raise energy efficiency with targets which they will make public and report on each year starting in July 2008.
Leading international groups with high energy consumption including Alcan, Anglo-American and Rio Tinto were among 100 large companies to adopt the "Caring for climate" declaration at the United Nations' Global Compact meeting in Geneva.
A further 150 small and medium-sized companies, including a number from China and other emerging economies that are becoming large energy consumers also signed up.
Georg Kell, head of the Compact, a grouping of more than 3,100 companies convened by the UN since 2000, said the move represented an "unprecedented effort" by businesses to fight global warming, building on some national initiatives such as that within the US.
While the declaration itself did not set any numerical targets, it committed members to publishing their own and provided a framework to hold them accountable.
Sir Mark Moody-Stuart, chairman of Anglo-American and a member of the Compact's advisory council, praised the declaration while adding that "I don't believe it goes far enough."
He said his own group had already pledged to cut emissions by 15 per cent by 2015 and was having difficulties in achieving that goal.
The UN Global Compact has been criticised by some non-governmental organisations for providing a public relations shield for companies while failing to substantially meet its environmental, social and anti-corruption goals partly because it has little enforcement power.
However, Mr Kell said that after lengthy internal discussions, his members had agreed to add "teeth" by evicting last year 500 of some 4,000 companies that had initially signed up but then failed to meet its objectives. He said a further 500-700 would be kicked out this year.
The participants in Geneva also issued a general declaration committing members to continuous improvement in human rights, labour conditions, the environment and anti-corruption. The "Geneva declaration" said they would "strive to give concrete meaning to a principles-based approach."