New car sales fell for the 10th month in a row in April, according to the Society of Motor Manufacturers and Traders (SMMT).
There were 137,746 new cars registered during the month, 7.4% down on the same time last year, when sales were boosted by the government's scrappage scheme.
Private vehicle sales were 23.5% lower last month. However, sales to business customers rose strongly.
The SMMT also warned of possible supply problems due to the Japan earthquake.
Fleet sales of 25 or more cars to big companies were up by 6.5%. Business sales to smaller firms of 24 or fewer cars were up by 12.1%.
According to the SMMT, the market overall was 1.5% ahead of the industry forecast and, if scrappage sales were taken out of calculations, it was on a par with last year.
"New car registrations in April demonstrated continued stability in the marketplace with demand remaining lower than in 2010, although slightly ahead of industry expectations," said SMMT chief executive Paul Everitt.
The SMMT is still forecasting that for 2011 as a whole, sales will be 5% lower than 2010 at 1.93 million cars.
But it warned of uncertainty surrounding consumer confidence and "possible short-term supply constraints" caused by the earthquake and tsunami in Japan.
Japanese car companies Toyota and Honda have both cut UK output to manage the shortage of car parts coming out of Japan.
"The coming months will remain challenging but we do expect to see a return to growth in the second half of the year, " said Mr Everitt.
The SMMT has also published the latest figures on commercial vehicle sales. These show that total van and truck registrations in April rose by 24.1% to 21,578.
"If you look at commercial vehicles we've seen sustained increases in the purchase of light vans and heavy trucks really over the course of the last year.
"I think that does suggest that there is a strengthening business recovery and I believe that will begin to feed through into private sector demand as we move into the latter part of this year," he told the BBC.
In 2012, the SMMT expects car sales to exceed 2 million. Registrations hit a peak in 2003 when 2.56 million cars were sold.