A French government minister has said that the government is considering raising taxes on diesels in the wake of evidence that diesel emissions are more harmful than previously thought.

Environment Minister Segolene Royal told a French TV station that France is considering raising taxes on diesel over the next five years to end an advantage over gasoline and encourage drivers to choose cleaner cars.

Royal, who is also responsible for transport, has in recent weeks rejected calls to ban diesel or end its tax breaks, but on Sunday backed the idea of phasing out the fuel's tax advantage.

"We need to start preparing our move out of diesel right now," she told France 5 television. "We should phase out diesel's (tax) advantage over five years."

She said that the fuel tax levied on diesel was currently 0.15 euros per litre lower than on gasoline.

She also said that progressive increases in diesel taxes would be discussed during the debate on France's 2016 budget bill, and should be offset by tax breaks for cleaner-fuel vehicles.

France is calling for 25 “breathable towns” in five years with many cities coming forward with ideas to reduce pollution particularly related to road traffic.

“Thanks to setting up an air quality certificate, which will easily identify the level of vehicle pollution, 23 low-speed zones could be created by 2016 in France, with the help of the [Energy] Ministry, opening the way for a new generation of anti-pollution local policies,” said the environment department.