The price of petrol rocketed at the fastest rate for 18 years last month in a "hellish" May for motorists, a new report has revealed.

Motoring organisation the RAC said the cost of petrol went up by 6p a litre in May, the biggest monthly rise since it started tracking prices in 2000.

The organisation's report suggests the average UK petrol prices hit 129.4p a litre, while average diesel prices rose to 132.3p a litre.

The RAC said a "punitive combination" of higher crude oil prices and a weaker pound was to blame for the increases.

It pointed out that oil prices broke through the $80-a-barrel mark twice in May, a three-and-a-half year high.

And as well as the higher global market price of crude, the pound's current weakness against the US dollar was also making petrol more expensive as oil is traded in dollars.

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Prices at the pump rose by 6p a litre in May

The RAC said the average prices of both petrol and diesel had risen every single day since April 22, adding 8p a litre in the process. The motoring body said this was the longest sustained price increase since March 2015.

RAC fuel spokesman Simon Williams said: "May was a hellish month for motorists. Sadly, they have been besieged by pump price rises for three months with nearly 9p a litre being added to petrol since the beginning of March.

"The rising oil price, together with a weaker pound, is a punitive combination for anyone that drives regularly. 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.

"In the last week of May the oil price cooled a little to $76 a barrel which is slightly better news for motorists as the RAC's two-week forecast is currently showing that average prices may even reduce by a penny or so.

"While this isn't much, and could easily change in response to oil trading this week, it is at least a sign that the constant rise in forecourt prices may have stopped for the time being."

Howard Cox, founder of the FairFuelUK Campaign, said: "Current pump prices are 1p to 2p per litre more than they need be, despite escalating oil costs and the weaker pound.

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"Businesses in the fuel supply chain are yet again exploiting the already highest taxed motorists in the world by not reducing pump prices when oil prices fall.

"They rise like a rocket and fall like a feather. As a consequence, inflation, GDP and consumer spending is being impacted badly by these greedy companies."

The RAC has provided a regional breakdown of fuel price rises.

According to its research, the rise in the East Midlands in May was the second highest in the whole of the country, increasing by 5.96p to an average of 129.2p a litre. Only the North West saw a higher rise (5.98p).

In Derby, the cheapest place to buy petrol and diesel is Costco, where on average, the cost of fuel is a couple of pence cheaper - but to take advantage you have to pay for a Costco membership.

Elsewhere, the cheapest petrol stations in Burton and South Derbyshire, according to comparison website PetrolPrices.com , are as follows:

Cheapest petrol prices around Burton

Unleaded

Tesco, St Peter's Bridge, Burton - 126.9p

BP, Wellington Road, Burton - 128.9p

Morrisons, Wellington Road, Branston - 128.9p

Diesel

Tesco, St Peter's Bridge, Burton - 131.9p

BP, Wellington Road, Burton - 131.9p

Morrisons, Wellington Road, Branston - 131.9p

Cheapest petrol prices around Swadlincote

Unleaded

Sainsbury's, Civic Way, Swadlincote - 122.9p

Asda, Burton Road, Woodville - 123.7p

Morrisons, Sir Herbert Wragg Way, Swadlincote - 124.7p

Jet, Station Road, Ashby - 127.5p

Diesel

Asda, Burton Road, Woodville - 127.7p

Sainsbury's, Civic Way, Swadlincote - 127.9p

Morrisons, Sir Herbert Wragg Way, Swadlincote - 128.7p

Jet, Station Road, Ashby - 131.5p