The plate-change campaign in March saw new car registrations rise 17.7% year-on-year to 464,824 units.
The Society of Motor Manufacturers and Traders said only March 2004 saw registrations higher, by 2,130 units, since the introduction of the twice yearly plate change.
March's campaign is typically the biggest of the year, accounting for almost a fifth of the full year market. The result last month could suggest an expected total industry volume in 2014 of almost 2.4m units.
Since the start of 2014, new car registrations have risen 13.7% to 688,122 units.
The March result was "a surprisingly strong level of growth and a reflection of intensifying consumer confidence and the availability of great new products"," said Mike Hawes, SMMT chief executive.
"Given the past six years of subdued economic performance across the UK, there is still a substantial margin of pent-up demand that is contributing to a strong new and used car market.
"There has never been a better time to buy a new car thanks to attractive finance deals and advanced technologies that often make new cars cheaper to run. We expect the market to continue to perform positively for the rest of the year, albeit at a more modest rate."
Chris Sutton, managing director at Black Horse Motor Finance, said: "With the historic and continued low interest rates, which are also influencing improved sales through low rate finance, we would also expect to see increased use of car finance in 2014 by potential car buyers.
"Our own data for March shows record transactions with PCP continuing to be popular, especially for new car buyers."
Phil Harrold, automotive partner, PwC, said: “The threat of rising interest rates may act as a brake on demand in the future; hence my belief is that demand will return to more stable growth rates.
"One feature worthy of note is the growth in alternatively fuelled vehicles, which have risen 64% to 8,713 registrations, as motorists seek ever more fuel efficient vehicles.”