Retail giants Tesco, Marks & Spencer and Ikea are among a raft of high-profile companies to join a new environmental initiative launched by the Mayor of London.

The Green500 is one of two initiatives it is hoped will cut climate change emissions by three million tonnes by 2010, saving£300 million on energy bills.

The scheme will give practical support and awards to large businesses to help them become more carbon efficient. Companies will be given a carbon mentor, to help them implement a carbon reduction plan and will be awarded if they reach their targets.

Ikea UK environmental manager Charlie Brown said: “Ikea believes that leadership is key to achieving improvements in environmental performance, which is why we are one of the first companies to have signed up. We want to demonstrate that we can be a good business while doing good business.”

Initial membership of the Green500 costs companies£3,500.