Drivers of diesel vehicles could face restrictions on going into city centres under Government proposals to improve air quality.
The move would affect six cities in areas where air quality targets for 2020 are expected to be missed.
They are London, Birmingham, Leeds, Nottingham, Derby and Southampton.
The consultation document, launched by the Department for Environment, Food and Rural Affairs, states that local authorities in these cities should "consider the role of access restrictions for certain types of vehicles" to reduce nitrogen dioxide (NO2) emissions.
NO2 is estimated to be responsible for 23,500 deaths in the UK each year, while a further 29,000 are killed by particulates - which are tiny particles of soot.
Mayor of London Boris Johnson has already announced plans for an "ultra-low emission zone" in the capital from 2020.
The move will require all but the cleanest diesel cars already manufactured to pay an extra £12.50 each day they enter the congestion charge zone, on top of the standard fee (currently £11.50).
RAC spokesman Pete Williams said it was important to consider the impact that buses and taxis have on air quality, as well as private cars.
He also claimed it was unreasonable to punish motorists who were encouraged by the taxation system to buy small fuel-efficient diesel vehicles with a low carbon footprint.
"Banning cars from towns and city centres is potentially damaging for businesses and for individuals especially without any clear guidance on long-term solutions.
"Whilst we know there are air quality problems in a number of our cities, there is no consistent approach to a solution," he said.
"At the moment we can see proposals, like the London ultra low emission zone, that follow a measured common sense approach and others that demonise diesel vehicles without regard to the extent to which the vehicles concerned are contributing to the problem."
A Defra spokesman said: "None of the plans we are consulting on for cities outside London include restrictions on cars.
"The measures we are looking at include improving bus and taxi fleets to investing in cycling infrastructure and upgrading roads so they run more smoothly."