A group of UK businesses, including Aviva, Microsoft and BT, are calling for compulsory carbon reporting to be introduced by the end of the year.

The Aldersgate group of businesses has written a letter to business secretary Vince Cable, urging him to make carbon reporting a legal requirement.

Currently, almost two-thirds of the UK’s largest companies refuse to publish their carbon emission reduction targets.

“It is hard to see how the government’s green ambitions will be met without more robust measurement and reporting of carbon emissions,” said Peter Young, chair of the Aldersgate Group and author of the letter. “Carbon reporting is not a burden. It is about identifying cost savings and opportunities.”

The WWF-UK and the Co-operative Financial Services are also calling for mandatory carbon reporting.

A report from the two firms, published this week, highlighted that some major oil companies are facing billions of pounds in future carbon liabilities as the cost of carbon rises, highlighting the need for mandatory reporting, to make investors aware of any risks.

The UK government must introduce mandatory carbon reporting by 2012 under the terms of the Climate Change Act.