Demand for new cars fell for the eighth month in a row in November, according to figures by the Society for Motor Manufacturers and Traders, prompting it to warn declining sales are now a "major concern".
Some 163,541 new cars were bought during the month, an 11.2 per cent fall on the same period last year.
Diesel sales were hit particularly hard, falling almost a third year-on-year, while sales of petrol cars edged up by five per cent.
Meanwhile, demand for alternatively fuelled vehicles, which includes electric and hybrid engines, jumped 33.1 per cent.
The figures mean registrations of new cars have fallen by five per cent in the 11 months of 2017, with just under 2.4m new cars sold.
Mike Hawes, chief executive of the SMMT, pointed to falling business and consumer confidence as drivers of the fall, and hit out against Philip Hammond's crackdown on diesel cars in last month's Autumn Budget.
“An eighth month of decline in the new car market is a major concern... exacerbated by ongoing anti-diesel messages from government," he said.
"Diesel remains the right choice for many drivers, not least because of its fuel economy and lower CO2 emissions. The decision to tax the latest low emission diesels is a step backwards and will only discourage drivers from trading in their older, more polluting cars. Given fleet renewal is the fastest way to improve air quality, penalising the latest, cleanest diesels is counterproductive and will have detrimental environmental and economic consequences.”