London Mayor Boris Johnson, the telecoms group BT and 40 MPs have demanded that Gordon Brown introduces legislation to make big companies report their carbon emissions.
The coalition, led by the public affairs group Aldersgate, will deliver a letter to the Prime Minister tomorrow criticising the Government for watering down an amendment to the Climate Change Bill that demanded the legislation.
The Environment minister, Phil Woolas, said last week: "The Government is not persuaded that such specific mandatory requirements are an effective means of encouraging reductions."
However, the coalition's letter says: "We believe that a common protocol that is consistent with international reporting standards would be a significant driver for change and competitive advantage in the private sector."
Other signatories include Friends of the Earth, Christian Aid, the waste management company Biffa and the Institution of Civil Engineers.