UK diesel car sales fell by a fifth in July, according to the Society of Motor Manufacturers and Traders (SMMT), as public concerns over air quality continue to grow.

Recent news headlines have focused on possible inner city bans on diesel cars, particularly in London, and the fact that German car makers want to pay their customers to trade-in diesels for electric models.

Interest in switching to electric has grown in the UK too, where searches for second hand electric-powered cars have increased by 700 per cent, according to Autotrader.

UK motorists have traditionally been some of the keenest buyers of diesel cars in Europe, but voices within government are dissuading further take-up.

In November a diesel scrappage scheme was tabled by Sadiq Khan, the Mayor of London, while in February Chris Grayling, the transport secretary, urged drivers to "think hard" before investing in a diesel vehicle.

While there appears to have been a sharper fall in diesel sales in July, the class has been in steady decline for many years.

However, diesel fuelled cars still offer significant fuel economy savings for drivers who travel long distances. But in cities, where people make much shorter trips, diesel has fallen out of favour significantly. JLR reported a fall in diesel sales of 87.4 per cent in London across 2016.

Diesel cars – particularly older models – have been identified as producing NOx particles, which have been linked to poor roadside air quality and respiratory conditions. Previous governments had championed diesel take-up, before research highlighted health implications of the technology.