Small diesel and hybrid cars to lose congestion charge exemption Over the past decade diesel cars have soared because of the tax incentives they have enjoyed from 10 per cent of vehicles on the road to 50 per cent. But there has been mounting concern at other emissions, notably particulates, from diesel cars and the health risks they pose. Under the new plans, which are due to come into force in the summer only cars which emit 75 grams of Co2 per kilometre will be exempt from the charge. This will mean that only drivers of electric vehicles will no longer have to pay. It is estimated the change could raise as much as £2 million a year, but there was fierce condemnation from motoring organisations. It's disappointing for people who made the investment. It is a big outlay," said Paul Watters of the AA. Small diesel cars are not polluters and are ultra clean with particulate traps, causing minuscule harm to the environment.