THE Met Office's cutting-edge £80 million Westcountry headquarters – the home for weather forecasting and warnings on climate change – has been named as one of the worst polluters in the region.

Despite a number of so-called "green" measures, the Exeter building has been handed the lowest possible energy rating.

It is responsible for more than 12,000 tonnes of carbon dioxide a year – a car covering 9,000 miles a year produces three tonnes.

The figures have been revealed by the Department of Communities and Local Government which has published the ratings and emissions of every public building in the country.

Met Office spokesman Barry Grommett said their supercomputer – vital for both forecasting and climate change modelling – accounted for 75 per cent of its total power use.

"We recognise that it is big, but it is also necessary," he said yesterday. "We couldn't do what we do without it. We would be throwing ourselves back into the dark ages of weather forecasting if we withdrew our reliance on supercomputing, it's as simple as that."

Mr Grommett complained that the rating process was "fundamentally flawed" and argued that its carbon footprint was more than offset by the benefits that it delivered.

That included saving lives through severe weather warnings, while its forecasting for the global aviation industry saved an estimated 20 million tonnes of carbon dioxide every year. Its office space was also rated as "excellent" by the Building Research Establishment, he said, which recognised environmental features such as a passive air system instead of air conditioning, toilets flushed with grey water and high recycling rates.

Mr Grommett stressed that the Met Office was committed to "reducing carbon dioxide output" and had recently installed new lighting to cut power demand. It was also researching more efficient supercomputers and hydrogen fuel cells for other sites.

Friends of the Earth's Maurice Spurway said: "Life is full of ironies and I think this is one of those situations where we have no choice.

"There are lots of areas where we do have a choice, such as how often we fly and how we insulate our homes."

The new Government list put dozens of schools and college buildings across Devon and Cornwall at the bottom of seven energy-efficient categories

That also included the RNAS Culdrose air base, job centres in Redruth and Newton Abbot, the Tate St Ives art gallery and several University of Exeter buildings.

Larger public buildings have needed display energy certificates, detailing their emissions and comparing their energy efficiency to similar properties, since last October.

The biggest polluters were the region's big hospitals. The main Derriford Hospital building in Plymouth accounted for 21,000 tonnes of carbon dioxide, the Royal Devon and Exeter Hospital 14,000 tonnes and the Royal Cornwall Hospital at Truro 11,800.

Marcus Dunstan, corporate maintenance manager for Cornwall Council, which owns 1,500 buildings, said energy management had been a "high priority" for more than 20 years.

Measures included energy management systems in larger buildings while a team of energy managers and technicians were currently being recruited. He said: "Every time we have a major, total replacement, whether that's a roof, windows, lighting or heating, we take the opportunity to put in something much more efficient and we have done that for the past 20 years."

In the case of the Carn Brea leisure centre – rated in the lowest category – a new boiler and heating system were being installed as part of a £500,000 upgrade which would greatly improve efficiency.

A spokesman for Devon County Council added: "Energy consumption across our estate is constantly under review and we work hard to improve energy efficiency whenever and wherever possible."