There were a total of 163,357 new registrations in April 2013 - a 14.8% rise on the April 2012 figure, the Society of Motor Manufacturers and Traders (SMMT) said.
The April 2013 increase was the 14th successive monthly rise. It took the total of new car sales for the year so far to 768,555 - a 8.9% increase on the January-April 2012 total.
SMMT interim chief executive Mike Baunton said: "The UK new car market continues to perform surprisingly strongly, with volumes again increasing in April.
"While the headline increase was up almost 15%, there were more sales days this year than last."
He went on: "The UK continues to perform well ahead of the troubled eurozone as consumer confidence, regular purchase cycles, attractive finance deals and wider market factors continue to make new car buying favourable for motorists."
Private sales were up more than 32% last month and have grown more than 15% so far this year.
The best-selling model for April was the Ford Fiesta, followed by the Vauxhall Corsa and the Ford Focus.