He added that some experts are predicting a crude oil shortage as demand rises but producers do not increase their output.
The ever-increasing costs could have an environmental benefit, as hard-pressed motorists are more likely to consider switching to an electric cars, which are cheaper to run.
Mr Williams added: “Ever escalating fuel prices may help to speed up the switch to electric cars as that is a sure-fire way of avoiding the wallet-stinging feeling at the pumps.”
Although electric vehicles are currently more expensive to buy than internal combustion engine cars, the price gap is narrowing.
Battery vehicles also tend to be cheaper run, as charging them with electricity costs less than traditional fuels, and they benefit from lower tax and maintenance bills.
Last month transport minister Rachel Maclean said the the cost of buying and running an electric car will fall to the levels of petrol and diesel vehicles in four years.
However, some experts believe that on a total cost of ownership basis – which includes purchase price and running costs – they could already be cheaper for some types of driver, such as those in company vehicles regularly doing longer journeys.