According to press reports, a report by scientists and engineers from the University of Ulster, commissioned by the Road Haulage Association, found ultra low sulfur diesel produced up to 20 times more carbon dioxide than the fuel it replaced.
Just one week after Chancellor Gordon Brown issued a fuel tax cut on the fuel in his pre-budget report, the scientists found the new fuel was also less efficient, the Daily Mail reported.
Ultra low sulfur diesel produces 10% fewer miles to the gallon, meaning drivers would have to burn more fuel and pump out more exhaust fumes to cover the same distance, the report claimed.
The team's findings flew in the face of previous research on ULSD, which found it reduced the emissions of sulfur oxides, which cause acid rain, by up to two-thirds.
ULSD is also said to cut emissions of pollutants including carbon monoxide, nitrogen oxide and hydrocarbons.