The popularity of diesel continues to grow, with Italy on the verge of becoming the sixth European country to sell more diesel-powered than petrol-fuelled vehicles.

In September, a record 52.4 per cent of registrations in the country were for diesel cars, an improvement of five per cent on the previous rate of 47.3 per cent.

Analysts are now predicting that the total market penetration figure for this year will be 49 per cent, placing Italy in a position to join the club of European nations where diesel cars outsell petrol models.

Diesel is the most popular fuel in France, Spain, Austria, Belgium and Luxembourg, with a consistent boom across the continent driving sales up by an annual rate of four points.

Diesel's share of Western European car sales hit 40.3 per cent last year, a jump from 1998's penetration rate of 24.8 per cent.

Customers are drawn to the fuel by its lower cost and the enhanced performance of new vehicles. Carmakers appreciate the reduced amount of emissions produced by diesel-powered vehicles.

According to Colin Couchman, an industry analyst from Global Insight, the future extent of diesel's market share is dependent on the emissions performance of petrol before 2008, by which time the car industry hopes to have reduced carbon dioxide emissions of 120 grams per kilometre.

'If carbon dioxide average emissions of petrol vehicles don't improve substantially in coming years, diesel must grow to almost 80 per cent of new passenger sales in 2008', he said.

'But if petrol engines can reduce average carbon dioxide emissions with new technologies such as direct injection by 2008, the carbon dioxide goal could be achieved with a diesel share of sales of lower 55 to 60 per cent'.