Demand for new cars fell by 1.6% last month compared with October 2019, new figures show.
The Society of Motor Manufacturers and Traders (SMMT) said just 140,945 new registrations were recorded in the UK last month, making it the weakest October since 2011.
Restrictions in Wales as part of the country’s coronavirus “firebreak” accounted for more than half of October’s year-on-year losses.
There was subdued activity from businesses across the UK, with a 3.3% drop in the number of new cars being added to larger fleets than in October 2019.
Private registrations saw a modest increase of 0.4%.
Sales of battery electric and plug-in hybrid cars bucked the overall trend with rises across the UK of 195.2% and 148.7% respectively.
Total registrations during the first 10 months of the year were down 31.0% compared with the same period in 2019.
SMMT chief executive Mike Hawes said: “When showrooms shut, demand drops, so there is a real danger that with England today entering a second lockdown, both dealers and manufacturers could face temporary closure.
“What is not in doubt, however, is that the entire industry now faces an even tougher end to the year as businesses desperately try to manage resources, stock, production and cashflow in the penultimate month before the inevitable upheaval of Brexit.
“Keeping showrooms open – some of the most Covid-secure retail environments around – would help cushion the blow but, more than ever, we need a tariff-free deal with the EU to provide some much-needed respite for an industry that is resilient but massively challenged.”
Rachael Prasher, managing director of automotive magazine and website What Car?, said: “The UK’s new car market is heading for another tough couple of months, with a lockdown forcing dealerships to close doors for at least four weeks and Brexit looming just around the corner.
“While the month-long lockdown is a short-term issue for the industry, Brexit poses a much more serious long-term concern.
“With negotiations for a trade deal still possible, it’s vital the UK avoids a no-deal scenario which could add thousands to the list price of many new cars.”