The introduction of the new ‘64’ numberplate helped drive registrations of new cars up to 425,861 in September, reaching the highest level for a September since 2004.

Registrations for the year-to-date reach 1,958,196 – up 9.1% on January-September 2013.

September and March – the months of the plate change – together account for a third of a year’s registrations, but after an 18% surge in March, September’s more moderate growth indicates demand starting to level off, according to the Society of Motor Manufacturers and Traders (SMMT).

Chief executive Mike Hawes said: “September’s strong performance underlined the continuing robustness of the UK new car market, particularly in the context of last September’s bumper volumes.

“Demand for the new 64-plate has been boosted by intensifying confidence in the UK economy, with consumers attracted by a wide range of exciting, increasingly fuel-efficient, new cars.

“In the months since March – which saw an 18% jump in registrations – the growth has shown signs of levelling off as the market starts to find its natural running rate.”

Sue Robinson, director of the National Franchised Dealers Association (NFDA) which represents franchised car and commercial vehicle retailers across the UK, said: “The market remains significantly high with increased footfall and interest from consumers which show that the sector is stable and growing.

“Strong finance packages which allow consumers to budget for monthly payments and dealership incentives have fuelled demand and customers are continuing to opt for smaller, fuel efficient models. We are encouraged that the growth and stability of the market shown by the latest plate change will continue through the remainder of the year.”