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Petrol prices rose by 6p a litre in Maythe largest monthly improve for the reason that RAC started monitoring prices 18 years in the past.
Average petrol prices hit 129.4p a litre, whereas common diesel prices additionally rose by 6p to 132.3p a litre.
The RAC mentioned a "punitive combination" of upper crude oil prices and a weaker pound was accountable for the will increase.
It identified that oil prices broke by means of the $80-a-barrel mark twice in Maya three-and-a-half yr excessive.
As properly as the upper international market worth of crude, the pound's present weak spot towards the United States greenback additionally makes petrol costlier as oil is traded in .
The RAC mentioned the typical prices of each petrol and diesel had risen each single day since 22 April, including 8p a litre in the method. The motoring physique mentioned this was the longest sustained worth improve since March 2015.
RAC gas spokesman Simon Williams described May as "a hellish month for motorists".
"The rising oil price together with a weaker pound is a punitive combination for anyone who drives regularly," he mentioned.
"For many people, there is little alternative to the car for the majority of journeys they have to make, so it is therefore very difficult to avoid feeling the pinch of rising pump prices."
Mr Williams stated that the oil worth had since cooled a little, suggesting that the fixed will increase in the price of petrol may need stopped in the intervening time.
He additionally mentioned there was speak that the following Opec assembly in Vienna on 22 June may consequence in a change of coverage for the oil cartel, which has been proscribing provide to bolster prices.
"If a decision is taken to increase supply, it may provide some much-needed relief for motorists at the pumps in the UK," he additionally mentioned.
Brent crude fell $1.10 a barrel to $75.69 on Monday afternoon.