Diesel and supermini models are to lead the ‘55’ plate charge according to figures released today by the Society of Motor Manufacturers and Traders.

Next month the industry expects around 420,000 new cars to leave showrooms, making it the second busiest month of the year. The SMMT predicts that as fuel prices continue to soar, more buyers will be thinking small - and thinking diesel.

Despite a drop in sales as a whole, diesel new car sales continue to rise. From January to July, the market for diesels rose 4.9% from 489,272 to 513,275 units, compared to an overall market down 5.9%.

Demand for supermini models and small family cars has also soared. In 1997 superminis accounted for 575,597 units at a time when the average price of petrol was 61.8p per litre. At the end of 2004 unleaded cost 80.9p and sales of models like the Fiesta and Corsa had risen to 839,604 units, up by more than a quarter of a million.

Today, many forecourts charge more than 90p per litre. But while fuel prices continue to hit motorists, fuel consumption is improving. In 1998, a new car averaged 34.5 miles to the gallon; in 2004 this had risen to 37.8, an improvement of nearly 10%.

SMMT chief executive Christopher Macgowan says: “Fuel costs have risen steadily in the last decade and now petrol has breached the £4 a gallon mark for the first time. So, while the mantra for many September customers will be big and beautiful regardless of fuel costs, for many more bangs for your buck will be the priority.”