Vodafone has topped the Tomorrow's Value Rating (ICT) list of the top 20 greenest technology companies.
Seven of the firms in the top 10 are European, two are Asian and one is American. Vodafone beat off competition from companies including Nokia, HP and AT&T.
Organisations are rated on a number of criteria, and awarded a percentage score that determines their placing. Vodafone was in pole position with 60 per cent, followed by Nokia with 55 per cent and HP with 52 per cent.
The phone operator was commended for its "all-round sustainability leadership " and for implementing wide-ranging "governance mechanisms for sustainability issues".
The Two Tomorrows Group, which compiled the list, said that Vodafone had listened to feedback from stakeholders, and had a good record in developing services designed to help disadvantaged people.
"ICT companies are increasingly recognising the commercial opportunity that lies in helping other industry sectors to reduce their carbon footprint, and in using their technology to offer socially valuable services such as health monitoring or education," said Thomas Krick, senior consultant at Two Tomorrows Group.
"Vodafone is best positioned to turn some of the world's most pressing sustainability challenges into business opportunities, thereby combining positive impacts with the generation of shareholder value."
Panasonic, which was eighth on the list, was singled out for its reduction in carbon emissions, while the remainder were said to be "struggling to achieve significant reductions".
The results are generated from publicly available information, according to Two Tomorrows Group.
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