New UK new car registrations were down 2.8% in February from a year earlier, due to another decrease in the sale of diesel vehicles.
The Society of Motor Manufacturers and Traders, the industry's trade body, said sales totalled 80,805 in February.
Demand for diesels fell by 23.5%, while sales of petrol cars rose 14.4%.
However, last month's fall, which comes ahead of the key number plate change in March, was not as steep as the 9.7% decline seen in January.
Sales of alternatively-fuelled vehicles (AFVs) rose 7.2% year-on-year, driven by some new, smaller models coming on the market.
The strong growth in sales of petrol cars and AFVs has been unable to offset the move away from diesel, which has now slid to a 35.6% market share.
March figures for sales with the new registration are yet to be confirmed.