The Stop-Start system operates best in urban traffic. When the brakes are applied at traffic lights or in gridlock the engine cuts out. Press the accelerator and the engine cuts in again. No fuel is wasted when the car is stationary and no C02 fumes are released.

The system reduces fuel consumption by up to 10% in urban traffic, acccording to Valeo, the company which provides the technology for Citroen.

Citroen offers the StopStart system here at 17,000 for a 1.4 litre C3 on special order only but, like a many other companies, is considering reintroducing it as demand for greener cars grows.

VW predicts that in five years the Stop-Start system "may be as common as anti-lock brakes or electronic stability control".

Within the coming months BMW is planning to offer the technology in some of its 1-Series models with manual transmission and is expected to offer it in bigger models later. The Stop-Start version of the BMW 118i produces 140g/km of C02 compared to 178g/km for the current version. The Mini will also offer the system.

The technology is now more reliable than in the past and manufacturers see it as a way to meet EU guidelines on emissions.

The EU wants car makers to cut CO2 emissions to an average of 130g/km, from the current figure of 160g/km, by 2012.

Opel is understood to be considering introducing the system, inexpensive compared to hybrid technology, within the next two years. And Toyota has said it is highly probable the company will introduce the system.

Toyota had a Yaris with the system but not in the new model. Mercedes Benz is expected to offer Stop-Start next year.