Thousands of diesel cars still on the roads with vital pollution filters removed

All diesel vehicles built since 2009 have been fitted with a pollution-busting particulate filter. This cuts harmful emissions from the exhaust by up to 95 per cent, but they have a tendency to go wrong, clog up and cause breakdowns – at which point unscrupulous motorists often have the filters removed rather than paying for a costly repair.

An investigation by BBC Radio 5 Live found that the Driver and Vehicle Standards agency has caught 1,800 cars running without these vital filters in the last three years – but experts say that figure is likely to be significantly higher, and could be contributing to worsening air quality in towns and cities.