BT has answered the call to be more environmentally friendly and has made significant contributions to the formation of European Union codes of conduct for improving energy efficiency in the telecom and IT industries.

The company is developing the UK's biggest corporate wind power project outside the energy sector. The farms will be up and running in three years' time and will produce up to 250 megawatts of electricity for the firm by 2016. In the meantime, 98% of the company's energy requirements will come from renewable sources, including solar power and hydroelectricity. Employees say the company takes its commitment to the environment very seriously, giving it an 84% positive green score.

BT first set CO2 reduction targets in 1992 and has set a target to reduce by 2020 the group's worldwide carbon dioxide emissions per unit of BT's contribution to gross domestic product by 80% from 1996 levels. Employees agree that the firm meets its environmental targets year on year, giving BT a 77% score. They also understand what their company's carbon footprint is (74%). Both are top 20 scores.

BT has made a commitment to respond to the challenges posed by climate change, including developing new products and services that it claims will enable households to cut greenhouse emissions by half by 2020.

Carbon clubs encourage employees to get involved and regular initiatives raise awareness at home, in schools and in the wider community. BT aims to get 20% of its workforce engaged in reducing their carbon footprint at work and at home by 2012.

Employees say they receive regular communication on environmental issues (83%), the environment is an everyday consideration in the workplace (74%) and the company encourages them to participate in its community programme (82%, a score bettered by just eight others in our list).

A fuel challenge campaign has been launched with the aim of reducing consumption by 10% and the firm won a Transport for London Greenfleet award last year. Employees are given safe and fuel-efficient driver training and the firm has trialled hybrid, biofuel and electric vans.

Employees say their boss does not expect them to save the environment while they drive a gas-guzzling company car (77%) and they do consider the impact of work-related travel, giving an 81% green score, bettered by just seven other companies.