The European vehicle manufacturers association, ACEA, has responded to the survey by environmental lobby group, T&E , published last week, that found that average CO2 emissions from some manufacturers had actually gone up, rather than down.

An ACEA spokesman said that while it cannot comment on statements regarding individual manufacturers, it rejects the implication that the automotive sector does not do enough to reduce CO2 emissions from cars.

In a statement, ACEA said that the voluntary agreement it signed with the European Commission in 1998 contained an industry average CO2 reduction target as opposed to individual targets per manufacturer and, therefore, the industry's progress under the commitment should be assessed on an industry aggregate basis.

"Individual companies may show different results per year, depending on model changes and car production cycles," the statement said.

ACEA argued that the automotive industry's performance in reducing CO2 emissions has been hampered by counter-productive effects of EU regulations and market developments.

"The gross reduction of CO2 emissions by means of vehicle technology has been 22% or 38g/km, but was brought back to a net reduction of 13% because of the effects of regulations and market demand. The 1998 commitment states that these factors should be taken into account when assessing the 1998 commitment results, but so far this has not been done."

A spokesman said the effects of regulation are mainly the addition of safety and air pollution control technologies that add weight or reduce fuel economy in other ways.