Plummeting sales of new diesel cars helped push the UK new car market to its sixth consecutive monthly decline in September, down 9.3% to 426,170 new units registered, according to figures released by the Society of Motor Manufacturers and Traders (SMMT).

Diesel car sales were down 21.7%, while petrol cars were down 1.2%. However, demand for alternatively fuelled vehicles (AFVs) continued to accelerate in September, up 41.0% in the month and 34.6% year-to-date, with nearly 95,000 leaving forecourts this year.

Demand from business, fleet and private buyers all fell in September, down -5.2%, -10.1% and -8.8% respectively. Meanwhile, registrations fell across all body types except dual-purpose, which grew 2.4%. The biggest declines were seen at opposite ends of the market with both luxury saloons and superminis falling -36.4% and 21.2% respectively.

Year-to-date, new car registrations have fallen 3.9%, but overall, the market remains at historically high levels, and in September sales for the year topped than two million.

SMMT chief executive Mike Hawes said: “September is always a barometer of the health of the UK new car market so this decline will cause considerable concern. Business and political uncertainty is reducing buyer confidence, with consumers and businesses more likely to delay big ticket purchases.

“The confusion surrounding air quality plans has not helped, but consumers should be reassured that all the new diesel and petrol models on the market will not face any bans or additional charges. Manufacturers’ scrappage schemes are proving popular and such schemes are to be encouraged given fleet renewal is the best way to address environmental issues in our towns and cities.”