Across the country, the average price of a litre of unleaded went up by 2.74p in April to 123.20p. It was the greatest increase in well over a year, and the highest average price since November 2014.
Diesel shot up by an average of 2.94p a litre last month to 126.02p – meaning that it now costs more than at any time since December 2014.
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The RAC’s Fuel Watch data also uncovers some interesting regional variations around the UK.
Unusually, it was Northern Ireland that suffered the steepest increase in petrol prices last month, with a 3.47p rise taking average prices in the province to 122.94p a litre.
Yorkshire and the Humber had the cheapest average petrol prices at the end of April, at 122.48p a litre.
Meanwhile, the South East remains the priciest part of the UK for both unleaded petrol (124.05p a litre) and diesel (126.79p a litre).
RAC fuel spokesman Simon Williams says a 12% jump in the price of oil from $67 a barrel to $75 “cost motorists dear” in April.
“The cost of filling up an average family-sized 55-litre car with petrol is now nearly £68, which is £4.50 more expensive than it was last July,” he noted.
“For diesel car drivers it’s even worse with a tank costing over £69, which is £5.50 more.”
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And the outlook for fuel prices is “not good at the moment”, Mr Williams warned.
The key factor, he explained, is whether the United States re-imposes crippling economic sanctions on Iran – the third-largest oil producer in OPEC.
If this happens and supply drops, “motorists will end up paying far more at the pumps”, he said.
“Our current two-week prediction is for prices to go up by a penny or so, but this could quickly get worse if oil gets more expensive and the pound weakens any further.”