Supermarkets have been accused of rocket and feather pricing by the RAC in its latest monthly review of prices at the pumps.

Petrol prices at the pumps stayed flat in September, but diesel climbed by another penny to its highest point for more than four years, according to data from RAC Fuel Watch.

A 2ppl cut in petrol prices by the major supermarkets prevented a further rise, with unleaded ending the month at a UK average of 130.66ppl (130.75ppl – 3 September). Diesel, however, hit 134.41ppl – an increase of 0.93ppl, taking it to its highest since early August 2014.

RAC fuel spokesperson Simon Williams said: “While petrol prices were cut by 2ppl at the end of the month due to a lower wholesale price, the biggest retailers should have been passing on those savings on a regular basis rather than saving them up for headline-grabbing cut. Instead they were almost certainly hedging their bets based on the rising oil price and the fluctuating pound. This is sadly proof that rocket and feather pricing does exist among the major supermarkets.

“Latest market indications are showing prices are beginning to go the wrong way, perhaps taking us closer to the record highs of April 2012. We believe motorists have the right to expect the biggest fuel retailers to reflect the wholesale price more closely at the pump, as they purchase more frequently and therefore can easily do this. But that means moving prices down in a falling wholesale market as fast as they put them up when wholesale costs rise.”