Downing Street today refused to rule out the possibility of a UK network of toll roads in years to come.
It comes after a government source told The Times officials are taking the idea "very seriously" as fuel taxes fall.
Chancellor Rishi Sunak has suggested he could cut 58p-a-litre fuel duty - a huge earner for the Treasury - to help the cost of living.
At the same time, more people are switching to electric vehicles, paying no road tax and not buying petrol either.
That has left a dilemma for Mr Sunak in decades to come, as either taxes will have to be raised on motorists in other ways, or they will have to be spread out to other areas of the economy.
While toll roads are common place in many European countries, in the UK the biggest toll roads include the M6 near Birmingham where drivers have an alternative and it costs £7.10 for cars during the week, as well as £12.90 for HGVs, to use the road.
On the toll roads idea, a source told The Times: “It’s definitely being taken very seriously in Downing Street.
"The policy unit is giving it a thorough look and the problems with fuel duty now make it more urgent.”
Boris Johnson's official spokesman today refused to rule out the prospect, and suggested motorists will have to continue bearing the tax burden somehow.
Asked if No10 plans a network of toll roads in future years he replied: “We obviously keep taxes under review.
"And we are committed to ensuring motoring tax revenues keep pace with the changes brought about by the switch to electric vehicles and making sure the transition is affordable for consumers.
"But beyond that I wouldn’t get ahead of any fiscal matters.”
Asked about a more generic road pricing scheme he replied: “Again, this is something we’re keeping a close eye on.
"We know and we are encouraged to see a shift to electric vehicles.
"And we will need to make sure the tax system keeps pace with that.
"But it will be for the Chancellor and others to set out our approach.”
Asked if that means the overall tax take from motorists shouldn’t fall, he replied: “It will be for the Chancellor in the round to look at what is the right balance across the entire tax system to ensure we have well-financed public services in the normal way.”
Asked if he was basically saying any deficit in tax take from the move to electric has to be made up from somewhere, probably motorists, he replied: "That feels like more than what I just set out.
"What I’m saying is our tax system needs to take pace with the changes. Beyond that, it’s for the Chancellor.”
Another option which has been recommended by the cross-party Commons transport committee is for monitoring technology that would charge drivers a fee for the distance they have gone.
But there are fears that there could be a backlash to this especially if it is introduced in towns and cities.
The government is working at options with petrol and diesel cars being phased out and it is estimated that without them in 2030 then the Treasury would be losing £35 billion.
