The depreciation of the pound has increased drivers' fuel bills by 7 pence a liter over the course of a year, according to a government analysis.
A study conducted by the Competition and Markets Regulator (CMA) found that the "main reasons" for higher fuel costs were higher oil prices and improved profit margins at refineries.
A report published in July said the cost of oil, which is usually priced in US dollars, had risen by about 20 pence in UK fuel prices in the 12 months to June 27.
During the same period, the devaluation of the pound against the dollar resulted in an additional 7 pence per liter on fuel bills.
That was more than 5 pence per liter the Treasury had imposed on record prices in March.
The CMA found that the decline was generally carried over to retail traders.
The latest government figures show that the average price of a liter of petrol at UK shipyards is around £1.62, while diesel costs around £1.81 a liter.
A year ago prices were £1.37 for petrol and £1.41 for diesel.
On September 23, the pound fell to an all-time low against the dollar after then-foreign minister Kwasi Kwarting approved the mini-budget.
It has since recovered but is still 18% lower than it was a year ago.
Steve Gooding, director of RAC, an automobile research charity, said: “The CMA believes that the 5 pence tax cut announced earlier this year has reached drivers, but it has been absorbed by the sharp drop in the value of the pound. For motorists who suffer from high prices at their gas stations.
“While fuel prices have fallen significantly in recent weeks, higher crude oil prices, higher refining margins, an Organization of the Petroleum Exporting Countries (OPEC) cut in oil production and more turmoil in the currency markets suggest a storm is clouding the financial horizon. Diesel who are already facing a price premium of 20 pence per liter of the substance.
“Given all the other pressures facing the Treasury, it seems unlikely that another rate cut is imminent.
"If one is to come in, it has to be of a large size to have a huge impact on pump prices."
The authority also found that the widening gap between the price of crude oil entering refineries and the wholesale price of gasoline and diesel leaving refineries explains the increase in service prices by 24 pence per liter during the past year.
