Diesel drivers could be forking out up to £800 more in road tax if a think-tank were to get its way.
Policy Exchange is urging the Government to look at increasing vehicle excise duty (VED) for new diesel cars in a bid to improve air quality.
It says owners should pay more to reflect the higher level of air pollution their cars cause in comparison with petrol cars.
But RAC public affairs manager Nick Lyes disagrees with the proposals. He says: "The RAC recognises that improving local air quality is an extremely important issue, however the focus should be on encouraging owners of older diesel vehicles to switch to cleaner models.
"This could include new, cleaner diesels as a Euro 6 diesel vehicle emits significantly lower NOx and particulate emissions than a Euro 5 diesel. Cleaner diesel vehicles also have an important role to play in reducing CO2 emissions, which are the primary cause of climate change.
"It's also important to note that poor air quality is predominantly a local issue. The RAC feels that clean air zones, which specifically target areas where emissions are high, could be part of the solution to discourage older, dirtier vehicles from entering areas where nitrogen oxide emissions and particulates are at problematic levels. Efforts should also be made to clean up all vehicles that contribute to the problem, including older buses and taxis."
Policy Exchange claims increasing VED for diesel vehicles could generate an extra £500 million a year to fund a new diesel scrappage scheme. It believes matched funding from manufacturers could see motorists receive grants of £2,000 to get rid of an old diesel car or van and buy a lower-emission vehicle.
"If this proposal were to be adopted by the Government, it could cause a swing in demand that motor manufacturers might have difficultly handling because production capacity is geared to the current mix of petrol and diesel engines," adds Mr Lyes.
"It could also penalise light commercial vehicle purchasers whose vehicle duties are often far more suited to diesels because of the engine speed/torque relationships for diesels which allows a heavily loaded vehicle to pull away from a standing start at low revs."
Copyright Press Association 2016. Motoring News articles do not reflect the RAC's views unless clearly stated.