British new-car registrations rose by 6% in March to 492,774 vehicles — the best month since the twice-yearly number-plate changes were introduced in 1999.

The Society of Motor Manufacturers and Traders (www.smmt.co.uk) said that the increase took sales so far this year to 734,588 vehicles — a 6.8% increase on the same period of last year. March was also the 37th month of consecutive growth.

The SMMT said that new products and attractive finance packages — underpinned by low interest rates — helped to deliver the record result, which was led by the fleet sector, with 11.6% year-on-year growth.

SMMT chief executive Mike Hawes said: “The best month this century for new car registrations is a welcome boost for the UK’s thriving automotive sector.

"The challenge for the new Government and industry alike will be to maintain this momentum and to strengthen Britain’s manufacturing capabilities through continued investment, innovation and policies that maintain our global competitiveness.

"Whatever the General Election result, the new Government must keep up the commitment to the sector, which is delivering at home and abroad.”

Howard Archer, chief European and UK economist at the HIS investment group, said: “March’s gain is all the more impressive, given that the gains are now coming from a high base.

"However, it is unrealistic to expect car sales to keep achieving strong growth rates through 2015, considering that they are now at such an elevated level.”

Chris Sutton, managing director of motor-finance provider Black Horse, disagrees. He said: “The industry has for a while been suggesting that the demand for new cars will ease. However, based on current data, it is hard to predict when this growth will slow down.

"Certainly, the continued low-interest-rate environment, coupled with attractive and affordable car-finance deals, continues to play a strong role in maintaining growth in this part of the UK economy.”