The European Parliament's Green group has urged the EC to strengthen particulate emissions rules.

In an open letter to EC president Romano Prodi and environment commissioner Margot Wallstrom the group argued that a limit of 0.0025 g/km should be applied for 2010, noting that as many as 50 models already comply.

The letter notes the "urgent health risk in Europe caused by motor vehicle pollution, in particular by fine particle emissions from road transport".

The calls follow a growing emphasis on a low-emissions society, with the German environment secretary Juergen Trittin recently adding his weight to the argument.

Mr Trittin denied reports that a carbon dioxide-based car tax is to be introduced in Germany, but stressed the importance of controlling diesel emissions.

He said that his "absolute priority" at present is the fiscal promotion of diesel engine vehicles with particulate filters.