Drivers are paying out more at the pumps for petrol despite a dip in world oil prices, according to the AA.
Yet the need for fair pricing on forecourts has been largely ignored by politicians during the General Election campaign, the motoring group said.
Its figures showed the price of oil was 5% lower per barrel in the first two weeks of April 2015 than in the first two weeks of March 2015.
But average UK petrol prices rose from 111.92p a litre in mid-March to 113.29p a litre in mid-April.
Diesel also rose, with average prices going up from 118.19p in mid-March to 118.83p in mid-April.
Across the UK, the cheapest petrol, averaging 113.1p a litre, was currently available in London, in south east England and in Yorkshire and Humberside.
Scotland had the most expensive petrol, averaging 113.8p a litre.
Northern Ireland had the lowest diesel, at 117.7p a litre, while Scotland had the highest, at 119.6p.
AA president Edmund King said: “Cars are like blank cheques for whoever feels the need to balance the books by plundering drivers’ pockets.
“Motorists prop up the Treasury to the tune of 10% of the UK’s total tax-take, and now the fuel retailers are taking £3 a tank extra on diesel to steady their finances.
“Manifestos promise action and transparency on domestic energy bills, but nothing on road fuel price transparency.”