Since records began in 1990 levels of pollution have been reducing at an annual rate of a few percentage points.
But in 2009 the amount of carbon dioxide and other gases fell by 8.6 per cent, largely due to the contraction in industry caused by the recession.
Joan Ruddock, the Energy and Climate Change minister, said every sector, including homeowners, have contributed to the fall in pollution.
But Greg Clark, the Tory energy spokesman, said most of the fall was because of the recession.
“It is disappointing that it took the longest and deepest recession since World War II for Labour to achieve any noticeable fall in UK carbon emissions,” he said.