The vote to leave the European Union has put an additional 5p on a litre of petrol, the Liberal Democrats have claimed.
Nick Clegg, the party’s spokesman on Europe, said motorists were paying the price at the pumps for the post-referendum slump in the value of the pound.
The Lib Dems calculated that the average price of a litre of petrol had risen by 7p since the Brexit vote last June.
Of that, the party said, 2p was due to the increase in the international oil price with the rest down to the fall in sterling which followed the referendum.
It said the 5p “Brexit” increase worked out at £2.50 on a tank of petrol for an average-sized car, or £60 per year for the average motorist.
Mr Clegg said: “Theresa May claims that Brexit is going to be a great success. The reality is it’s going to make us poorer. The effects are already being felt.
“The rise in fuel costs will push up prices in the shops. This means consumers are going to be hit twice, once at the pump and again at the checkout.”