Petrol prices saw the highest monthly increase since the RAC began tracking prices 18 years ago, with average prices up 6ppl in May. Over the month, unleaded rose from 123.43ppl to 129.41ppl.
The increase in the average price of a litre of diesel was slightly greater at 6.12p from 126.27ppl to 132.39ppl but this was the second greatest monthly rise since the start of 2000, as diesel shot up 8.43ppl in May 2008, from 120.83ppl to 129.26ppl.
The RAC Fuel Watch, based on Experian Catalist data, also showed that the average prices of both petrol and diesel have gone up every single day since April 22, adding 8ppl in the process the longest sustained price increase since March 2015.
In May the big four supermarkets raised petrol by 5.49ppl and diesel by 5.88ppl, while on the motorway service stations added 6.37ppl to unleaded, taking it to 144.75ppl, and 6.69ppl to diesel making it 147.80ppl 15ppl above average UK prices.
The increases have been driven by a jump in the price of oil, coupled with a weakening of the pound against the dollar.