A league table compiled by the Guardian identifies EON UK, the electricity generator that owns Powergen, as Britain's biggest corporate emitter of greenhouse gases. It produced 26.4m tonnes of carbon dioxide last year - slightly more than Croatia did.
The figures, which have prompted new calls for tighter restrictions on corporate pollution, show that efforts by individuals and households to cut their carbon footprints will make little difference unless accompanied by greater action by industry. A 1% increase in the efficiency of the giant Drax power station in North Yorkshire - the largest in Europe and the single biggest polluting site in the UK - would save the typical carbon emissions of 21,000 households. Drax alone produced 20.8m tonnes of carbon dioxide last year.
The top five companies (EON UK, RWE Npower, Drax, Corus, and EDF) produced between them more than 100m tonnes of carbon dioxide in 2005. On average, the country's 26m private cars produce 91m tonnes each year.
The carbon dioxide emissions of more than 700 industrial sites across Britain are contained in figures released yesterday by the European commission. They detail the UK's participation in the first phase of a Europe-wide scheme intended to tackle climate change by capping the amount of carbon the heaviest polluters can emit. Companies failing to hit a target - applying to emissions from onsite activities such as combustion only - must buy permits to pollute from rivals that have successfully cut emissions. Critics said the first phase of the trading scheme has made global warming worse by giving European companies more permits than needed.
Britain was an exception, however. Its participating companies, which had lobbied for laxer targets, produced together more than 242m tonnes of carbon dioxide - they had permits to emit only 209m.
Germany negotiated to produce 495m tonnes of carbon dioxide, but its companies emitted only 474m. France produced 131m tonnes, but had permits for 151m.
A spokeswoman for EON said: "We are one of the leading green generators and invest more per customer in green energy than any other major supplier in the UK." A spokesman for RWE Npower said: "We're one of the UK's biggest power generators, so of course we're going to have more emissions than, say, a single power station somewhere. The test of 'green-ness' is how much you are changing."
Hundreds of UK companies are excluded from the scheme - because they are not classed as big polluters or because they participate in a parallel system run by the government. Figures from these firms have been obtained by the Guardian under freedom of information laws. They show that dozens of household names produce more than many small countries.
British sites operated by Tesco, Walkers, Ford, Unilever, Kellogg's, Allied Bakeries, Nestle and Cadbury Trebor Bassett are among those that emitted more than 100,000 tonnes of CO2 in 2004 - more than that of Vanuatu, the Pacific state where 100 people became the first official climate refugees when they were moved from their coastal village in December.