Retail petrol sales for the period January to June dipped 5.8 per cent, or nearly 512 million litres, compared with the same period last year, Government figures highlighted by the AA showed.
But diesel sales for the first half of this year rose 6.6 per cent, or by nearly 270 million litres.
The AA said the petrol sales in the first six months of 2013 were more than 25 per cent lower than in the first half of 2008, just before the credit crunch.
Diesel sales in the first half of this year were 3.6 per cent higher than in the January-June 2008 period.
AA president Edmund King said: “It would be too easy to blame the collapse of UK retail petrol sales on car owners switching from petrol to diesel engines.
“These new Government fuel retail sales figures, when set against changes in the number of petrol and diesel cars on the road, show that soaring fuel prices have had by far the greater impact on pump sales since 2008.
“For five years, up to 76 per cent of AA members have cut back on car use, or on other spending or both, to survive petrol pump prices that peaked at 119.7p a litre in the summer of 2008 but then set the current record of 142.48p in April 2012.
“That is why it is critical for pump prices to drop as quickly as wholesale costs allow. The financial well-being and survival of drivers, consumers, business, Government duty revenue and, yes, fuel retailers depend on it,” said Mr King.
Asda announced a drop in its forecourt prices for petrol of two pence a litre days ago, with a drop of one pence a litre for diesel prices.
Their fuel prices are set nationally, but rivals Tesco announced a price reduction of up to two pence a litre at its own forecourts shortly afterwards.
The fall in wholesale costs of crude oil has been credited partly on increased stability in the Middle East, as the threat of military action against Syria appears to have receded.