Sales of cars made in the UK fell 6.3 per cent in January, as a decline in demand for diesel cars continued to put off buyers.
Some 163,615 new cars left showrooms in January, according to the Society for Motor Manufacturers and Traders (SMMT) - making it the worst January for car sales since 2014, when just over 150,000 new vehicles were sold.
Although registrations of petrol and electric and hybrid vehicles rose 8.5 per cent and 23.9 per cent respectively. they failed to make up for the drop in demand for diesel cars, which fell 25.6 per cent as politicians cracked down on polluting vehicles.
However, the SMMT added that last year, more than two in five cars which rolled off UK production likes were diesel cars.
"The ongoing and substantial decline in new diesel car registrations is concerning, particularly since the evidence indicates consumers and businesses are not switching into alternative technologies, but keeping their older cars running," said Mike Hawes, chief executive of SMMT.
The news came after figures showed European car sales reached their highest in a decade last year, rising above 15m, suggesting car manufacturers will call for early clarity in Brexit negotiations.
"January marked a 10th successive decline of falling car sales, thereby clearly pointing to a serious loss of momentum in the sector," said Howard Archer, chief economic adviser to the EY Item Club.
"The fact that car sales have fallen year-on-year every month since April 2017 points to a clear weakening underlying performance.
"[The year] 2018 looks set to be another challenging year for new car sales with a further drop of five per cent or more highly possible The sector is pushing very hard for early agreement on a Brexit transition arrangement to help ease uncertainties."