Environmental groups and companies including PepsiCo (PEP.N), Microsoft (MSFT.O) and Marks & Spencer (MKS.L), working together as the Aldersgate Group, called on the UK to speed up plans to enforce carbon emissions reporting requirements.

Business accounts for nearly a third of Britain's greenhouse gas emissions, and the introduction of mandatory emissions reporting would encourage companies to better manage and reduce their carbon footprints, the alliance said in a statement released on Sunday.

Under the Climate Change Act 2008, the British government is required to propose regulation on emissions reporting to help Britain achieve its climate objectives or to explain to Parliament why no such regulation has been made.

The Conservative-led coalition missed an April 6 deadline to take a decision, however, saying it needed more time to assess how to proceed after receiving more than 2,000 replies to a public consultation.

In a letter to Deputy Prime Minister Nick Clegg, the Aldersgate Group urged the government to clarify its position and make a swift decision.

"The introduction of mandatory (greenhouse gas) reporting would help to ensure greater accountability and transparency; create a level playing field, and help enable investors and consumers to make meaningful comparisons," it said.

Peter Young, chairman of the Aldersgate Group and author of the letter, said mandatory reporting was needed because voluntary efforts had run their course.

"Ironically, it would simplify the burdens on responsible businesses for the government to now signal a single mandatory requirement," he said.

In an online poll commissioned by the Aldersgate Group, more than 75 percent of 2,044 adults surveyed across the United Kingdom late in April said large businesses should be required to report carbon emissions.

Colin Baines, campaigns manager at The Co-operative group, the UK's largest mutual retailer, said mandatory reporting should be introduced as soon as possible, given that it has support from both business and the public.

"We have been doing this for over a decade, and if other large businesses still aren't voluntarily reporting, it is unlikely they ever will," he said.

(Reporting by Jeff Coelho, editing by Jane Baird)

• A Permanent Economic Emergency