New industry figures show that 215,312 cars were registered in September. That is more than a third less than the same month last year, which was already low because of the pandemic. In Scotland, there was a 30.2 per cent year-on-year fall to 19,395 registrations.
The latest result marks the weakest September since 1998, according to the Society of Motor Manufacturers and Traders (SMMT),which compiles the monthly data.
Yet the news was better for sellers of electric cars, who managed to shift nearly as many vehicles in just one month as they used to do in a year.
The data showed that 32,721 battery electric vehicles (BEVs) took to UK roads for the first time last month. It is just 5,000 less than for the whole of 2019, and BEVs now make up 15 per cent of the market.
The Tesla Model 3 was the best selling of all cars last month, followed by the Vauxhall Corsa and the BMW 3 Series.
SMMT chief executive Mike Hawes said: "This is a desperately disappointing September and further evidence of the ongoing impact of the Covid pandemic on the sector.
"Despite strong demand for new vehicles over the summer, three successive months have been hit by stalled supply due to reduced semiconductor availability, especially from Asia.
"The rocketing uptake of plug-in vehicles, especially battery electric cars, demonstrates the increasing demand for these new technologies,” he added.
Alex Buttle, director of used car marketplace Motorway.co.uk, said: “Despite the ongoing supply challenges facing the UK car industry, the industry was pinning its hopes on robust new car sales in September, with the reg plate change kickstarting demand growth alongside the surging used car market, which is already super-buoyant with sales continuing to accelerate.
“But with data showing that last month was the worst number plate change for new car registrations on record, these hopes have been somewhat dashed.
“The used car market will continue to benefit from disenchanted buyers who are unwilling to wait for a new vehicle.”