Motorists are facing further rises in petrol costs.
The price at the pumps has been pushed up steadily since the year's start by the increasing wholesale price of petrol.
As the fuel is traded in US dollars, traders get less petrol for their cash when the pound is performing weakly.
Experts have also blamed increased refining costs for an upturn in prices.
John Franklin, RAC spokesman, explained: "The wholesale price has been increasing since the start of the year. If that price goes up you are going to feel it at the petrol pumps.
"The weak pound is also a factor. Oil is traded in dollars - if the pound is weak you get less oil for your money."
The price of crude oil plays a key role in what we pay for petrol. In July 2008 oil soared to 147 US dollars per barrel.
This prompted unleaded petrol to reach an unprecedented 119.7p per litre.
On top of these factors, petrol is also subject to various taxes, duties and VAT - a 3p rise in petrol duty is due to come in on April 1.
Mr Franklin added: "In the short term, I'm afraid it's only going to get worse for the motorist."
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