Fuel duty could rise for the first time in a decade in next month's Budget, it has been reported.
Boris Johnson's top adviser Dominic Cummings is said to have demanded a hike in taxes for Britain's 37 million drivers - by ending a freeze that has lasted since the Tories took power.
A Treasury source would neither confirm or deny any details of the Budget.
During the election, the Prime Minister said he had "absolutely no intention" of ending the fuel duty freeze.
But the most recent year of the freeze alone - excluding the cost of all eight previous years - will cost the Treasury £4.4bn over five years.
By comparison, Boris Johnson announced £5bn last week for buses and cycling put together.
Meanwhile the PM is trying to appear to lead the way on the environment - and needs funds for the massive infrastructure drive demanded by Tory MPs in the Midlands and North.
According to The Sun, the tax is set to go up by around 2p a litre but could be delayed until next year.
That's in stark contrast to previous reports in August last year - which claimed the first Budget under Boris Johnson would actually cut fuel duty.
It comes as new Chancellor Rishi Sunak prepares to deliver his first Budget on March 11 just weeks after his predecessor Sajid Javid quit in a row with No10.
Downing Street has since set up a joint team of economic advisors to work "without a cigarette paper" between the Prime Minister and the Chancellor.
That suggests Mr Sunak - who has only just got his feet under the desk, and accepted the joint team as a condition of the job - is more likely to bow to demands from 10 Downing Street.
