The Department for Transport (DfT) says it has no plans to change its policy towards diesel cars following reports that up to 15 UK local authorities are considering charging diesel cars to enter city centres.
Sales of diesel have been growing and have overtaken declining petrol as the biggest selling fuel, but now local authorities are looking to curb diesel use over pollution fears.
Some city centres are struggling to meet EU directives over air quality and diesel exhaust is being seen as part of the problem.
London Mayor Boris Johnson wants to introduce an Ultra Low Emission Zone by 2020 and is proposing charging diesel drivers an extra £10 to enter on top of the congestion charge.
A DfT spokesman said it was committed to meeting EU air quality standards but it had no plans to change its policy towards diesel cars.
He said local authorities had powers to introduce low emission zones and this was a matter for them.
PRA chairman Brian Madderson said that if studies suggesting particulates from diesel exhaust fumes were more harmful than petrol fumes were correct, then he could understand why curbs were being considered.
He said: “Local authorities have an obligation to try to reduce fumes and one way is a financial penalty like this.
“What we do not want to see is any move to alter duty to make diesel more expensive.”
However, the RAC foundation said government incentives, such as putting diesel cars in lower vehicle excise duty bands, were to blame for the proliferation in diesel vehicles.
Foundation director Professor Stephen Glaister said: “This isn’t quite a mis-selling scandal, but for years ministers took their eye off the ball and encouraged drivers to buy diesels to help fight climate change.
“That has come at a cost: local air pollution. Today 10 million cars in Britain are powered by diesel engines - a third of the total.
"Part of the problem is regulation. In laboratory conditions diesel cars have met strict test criteria. Unfortunately that performance hasn’t been matched on the road and now we have a significant health issue because of the dash for diesel.”