TURNING the clocks back each winter increases Britain's greenhouse gas emissions and adds millions of pounds to power bills, according to a new study.

Cambridge University researchers estimate that darker evenings cause domestic consumers to use 2% more electricity, generating millions of tons of carbon dioxide.

Elizabeth Garnsey, one of the authors, and a Reader in engineering and business at the university's Institute for Manufacturing, said the study anticipated next weekend's turning back of the clocks one hour from British Summer Time (BST) to Greenwich Mean Time (GMT).

Under GMT, around 35% of the population are asleep when the sun rises in winter and so make no use of the extra daylight, she said.

When they come home from school or work in cold and darkness, they cause a surge in demand.

"Britain can only meet these daily surges by switching on less efficient back-up generating plants such as oil-fired power stations.

"We estimate that pushes up costs to 5% more than it otherwise would be."

Emissions

Dr Garnsey said: "Our current time policy costs us dearly in bills and carbon dioxide emissions.

"Setting the clocks back to GMT is an institutional practice so well entrenched it is exempt from evidence-based policy making. No systematic evidence has been produced and no research commissioned in support of the Government's position."

The report says that from 2001 to 2006 a 2% increase in average daily electricity consumption is estimated to have occurred during GMT months, over and above expected consumption if the clocks had not gone back.

Reckoned cumulatively since the re-imposition of GMT after a three year trial in 1971, being on GMT+1 in winter could have supplied the population of Greater London with electricity for two years at current consumption rates, it says.