Carbon reporting is becoming mandatory for all businesses listed on the main market of London Stock Exchange and may extend to all large businesses. BP, Tesco and Tate & Lyle are some of the names that will be affected.

Nick Clegg announced at the Rio+ 20 Summit today that Britain’s largest companies will have to publish full details of their greenhouse gas usage from April 2013.

A government review in 2015 could see this extended to all large public UK businesses.

Tom Delay, chief executive of the Carbon Trust said: “Today’s announcement is welcome news.

“Mandatory carbon reporting for companies listed on the London Stock Exchange from April 2013 will encourage even more businesses to reap the benefits of accurately understanding their carbon emissions.

“Measurement helps businesses to gain insight to help them take the right strategic decisions to ensure long term success.”

Nick Clegg’s article in the Guardian yesterday said the policy aims to make companies aware of their effect on the environment by measuring their emissions.

"Using resources responsibly is in business' own interests too," writes Clegg.

“But while nine out of 10 say sustainability is fundamental to their success, only two out of 10 record the resources they consume."