Only a quarter of Europe's 20 top-selling carmakers are on track to meet EU targets for cutting exhaust pollution, a survey revealed today.
The European Commission warned last month that it would impose legislation if car manufacturers failed to voluntarily reduce average CO2 emissions from new cars to 140 grams a kilometre by 2008, and to 120 grams by 2012.
But today's report shows that only five - Fiat, Citroen, Renault, Ford and Peugeot - are currently cutting emissions at a rate which will achieve or exceed EU requirements.
Fiat is the only manufacturer that has already reduced average emissions from its new models to below 140 grams a kilometre.
In contrast, Volkswagen, Europe's biggest car brand in terms of sales, has improved fuel efficiency at less than half the rate needed, according to the report by the UK's Institute for European Environmental Policy
Nissan, lowest-ranked of the 20 brands surveyed, has managed only 20% of the necessary emissions improvements.
Other manufacturers at the bottom of the table included Suzuki, Mazda, Audi, Volvo, BMW.
The figures were compiled for the Brussels-based Transport & Environment (T&E), which campaigns for sustainable transport.
The organisation said the survey struck a blow for transparency and accountability in the wake of a European Commission pledge not to publish the progress of individual companies in cutting emissions.
The pact was part of the voluntary CO2 emissions deal, which today's figures make clear is far from being met.
Even Toyota, lauded for its fuel-efficient, clean hybrid engine technology in the Prius, has achieved only 76% of the average CO2 reductions it should have made by now to keep on target.
T&E said Renault, Europe's second biggest brand, wason track to meet the targets, having reduced average emissions by twice as much as rival Volkswagen, while Ford and Peugeot had achieved well over 90% of emissions cuts they should have managed at this stage.
Aat Peterse of T&E said: "Clearly the target is achievable, but as long as carmakers go unpunished for their failure, we will never make the necessary progress.
"Europe must kiss its voluntary targets goodbye and come up with legally-binding measures to double fuel-efficiency in the next decade. Individual carmakers must be held responsible and punished if they fail."
The current targets are already weaker than targets set a decade ago by EU environment ministers, who called for a 120 grams maximum for new cars sold in Europe by 2005, or 2010 at the latest.
The slipping timetable has embarrassed the European Commission, which was forced to admit last month that its own fleet 85 limousines push out almost twice as much pollution as the proposed limits - an average 258 grams a kilometre
