Some 189,505 cars were registered last month, which is the most in April since 2003, the Society of Motor Manufacturers and Traders (SMMT) said.
April's performance follows a bumper March in which more than half a million cars were sold - the second-biggest monthly total on record.
SMMT chief executive Mike Hawes said: "After such a strong March, April's steadier performance was to be anticipated and is in line with our expectations for the year.
"Consumer confidence remains high as buyers continue to capitalise on attractive finance deals, although this could be affected by political and economic uncertainty in the coming months."
Year-on-year Volkswagen car sales suffered a 9.7% slide as the German manufacturer continued to suffer as a result of the diesel emissions scandal.
The brand had 16,877 registrations in April, compared to 18,690 in the same month in 2015.
Its year-to-date sales for 2016 are 6% down on the same point last year.
Volkswagen Group admitted last September that 482,000 of its diesel vehicles in the US were fitted with defeat device software to switch engines to a cleaner mode when they were being tested for emissions.
The Wolfsburg-based manufacturer announced that 11 million vehicles were affected worldwide - including almost 1.2 million in the UK.
Other VW brands had mixed results in April.
Year-on year sales for Audi were up 3.1%, but SEAT was down 0.7%, and Skoda fell by 1.1%.