Motorists will be forced to pay an extra 10-cents per litre on fuel purchased within Australia, if large oil companies get their way.

Major oil refiner Caltex is suggesting that all motorists be hit with a 10-cent per litre carbon tax to reduce the effects of climate change, and encourage more people to take public transport.

While the idea was first suggested last year, it is now clear Caltex and other oil and petrol suppliers are considering the plans more seriously.

News Limited newspapers reported that Caltex believed the carbon tax could reduce demand for fuel in times when the supply has most likely peaked.

"Every time motorists filled up at a service station, there would be awareness of the carbon tax, encouraging motorists to think about driving less, taking public transport or buying a smaller car when possible," Caltex spokesman Frank Topham said.