Demand for new cars fell by around 20% in September, according to an industry body.

The Society of Motor Manufacturers and Traders (SMMT) said around 339,000 new cars were registered during what is normally one of the industry’s strongest months due to the release of new number plates.

Diesel and petrol registrations were down year-on-year, with a modest rise for alternatively fuelled cars such as pure electrics and hybrids.

The SMMT said the decline was mainly due to changes to the way new cars are tested, with tougher emissions regulations introduced in the European Union.

The organisation’s chief executive Mike Hawes told BBC Radio 4’s Today programme: “This year we’ve had the first major change in the way you test vehicles – the first change in about 30 years.

“That has led to some major challenges in terms of supply because you’ve got to change the entire European model range, put them through the test, and that takes a considerable amount of time.

“Some manufacturers have had short supply which has meant sales have been down.”

Mr Hawes added that “demand is down a bit” due to a drop in business and consumer confidence due to uncertainty over Brexit.