Imperial College London and the vehicle analysts at Emissions Analytics teamed up to look at harmful NOx emissions in the exhaust emissions of a sample light-duty diesel vehicles which meet the Euro 4 and Euro 5 standards.

Of the ten cars in the sample group, all failed to meet Euro 4 and Euro 5 emissions limits, while only one was in line with the Euro 3 standard which came into force in January 2000. Average NOx emissions across the group were almost four times higher than Euro 5 requires, while Euro 6 will set an 80% reduction in NOx emissions for all type approvals after September 2014, and new registrations from January 2015.

Produced primarily by diesel engines, NOx emissions can cause breathing problems and premature death, the reasons behind the EU’s recent legal proceedings against the UK. Emissions of NOx were above January 2010 limits in 16 areas of the UK, with studies showing London would be unable to meet these targets until 2025.

In a statement published with the report, Emissions Analytics said: ‘NOx and miles per gallon standards are calculated using the New European Drive Cycle, the shortcomings of which have been widely reported and are supported by Emissions Analytics' large volume of real-world data.

‘Others have voiced concerns regarding the number of monitoring stations and the use of modelled data in EU Air Quality Directive compliance assessments. What it is clear is that real-world data has an important part to play in policy making.’