Registrations of new cars fell by 6.0% last month, figures show.
Industry body the Society of Motor Manufacturers and Traders (SMMT) said 144,288 new cars were registered in October.
That compares to 153,529 during the same month last year.
The SMMT said the decrease is equivalent to a £350 million loss in turnover.
The fall was driven by double-digit drops in petrol and diesel vehicle deliveries, down 14.2% and 20.5% respectively.
There was a 1.6% decline in the uptake of hybrid electric vehicles (EVs), and a 3.2% fall in registrations of plug-in hybrid EVs.
Pure battery EVs bucked the trend with growth of 24.5% amid the introduction of a raft of new models and heavy discounting.
The SMMT said the number of pure battery EV models available has increased by 38% since the start of the year to more than 125.
SMMT chief executive Mike Hawes said: “Massive manufacturer investment in model choice and market support is helping make the UK the second largest EV market in Europe.
“That transition, however, must not perversely slow down the reduction of carbon emissions from road transport.
“Fleet renewal across the market remains the quickest way to decarbonise, so diminishing overall uptake is not good news for the economy, for investment or for the environment.
“EVs already work for many people and businesses, but to shift the entire market at the pace demanded requires significant intervention on incentives, infrastructure and regulation.”
Ian Plummer, commercial director at online vehicle marketplace Auto Trader, said: “October new car sales are lagging, although electric vehicles are taking a bigger share of the market thanks to heavy discounting.
“The subdued petrol and diesel sales are also likely to be driven by the efforts of manufacturers to hit EV sales targets under the zero emissions vehicles (Zev) mandate.
“Manufacturers are making significant efforts to bridge the price gap to electrics – as shown by the 12% discounts on Auto Trader’s site in October – but the market is still not achieving the volumes needed.”
The Zev mandate requires at least 22% of new cars sold by each manufacturer in the UK this year to be zero emission, which in most cases means pure electric.
The figure will rise to 28% in 2025.
Manufacturers face being required to pay the Government £15,000 per polluting vehicle sold above the limits, or purchase credits from rival companies.
The SMMT said pure battery EVs represented 18.1% of the new car market during the first 10 months of the year.
Dan Caesar, chief executive of campaign group EVUK, said: “Discounting – taking place across all fuel types – is moving new car buyers towards battery electric vehicles as they become more affordable. A win for consumers.
“The Government’s strategy is working, and we urge them to resist calls to slow progress as the UK is now the second most successful EV market in Europe.”
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