Speaking at the environmental conference in Paris, Valls said transport accounted for a quarter of greenhouse gas emissions in France, and that the country’s long-running preference for diesel engines has been 'a mistake'.

Next year taxation will be reformed to remove the advantage for diesel compared to petrol, and Valls announced the incentives against plug-in vehicles would be maintained for five years, supported by additional charging points. An identification system marking out the most polluting vehicles will also be introduced next year.

‘In France, the diesel engine has long been favoured,’ said Valls. ‘It was a mistake. The government will set up in 2015, a vehicle identification system based on their pollutants emissions. This system will help communities develop policies promoting cleaner vehicles.’