Motorists are being fleeced at the pumps due to high fuel taxes and retailers that are reluctant to pass on savings despite plunging oil prices, campaigners have claimed.

New research has found that despite a 25 per cent drop in the price of Brent Crude last year, some forecourts tripled their profits with margins peaking at as much a 12.5p a litre on diesel last mont.

FairFuelUK, which commissioned the study, said it showed the current decade-low oil prices are not being passed on to UK motorists.

It is concerned that Chancellor George Osborne is set to break the fuel duty freeze and increase it by inflation, further hitting UK motorists who already pay the highest fuel duty of any drivers in Europe.

The group's Howard Cox said: “UK drivers should have seen much more significant falls in pump prices given the collapse of oil and thanks to greedy opportunism Christmas saw us paying an extra £5 retailer profit on every family car fill-up.”

Petrol prices now average 101.8p per litre while diesel sells for 102.8p, the lowest levels since January 2009.

An Office of Fair Trading investigation on the road fuel market, called by FairFuelUK, has found no dysfunction or profiteering and no further investigation is needed.

The group's spokesman, former Top Gear presenter Quentin Willson, said: “These inflated margins over Christmas speak for themselves. Fuel retailers are clearly taking extra profits while the oil price falls and definitely not passing them on to families and businesses. And the government seems to be turning a blind eye.”

While petrol prices in the UK are the second lowest in Europe before tax, they become some of the highest in the union when duty and VAT is added.

According to figures released last year, 70 per cent of the total price of petrol at the pumps was tax, leading to calls for cuts in fuel duty.

A Treasury spokesman said: “The Government cut fuel duty by 1p per litre in March 2011 and has cancelled all further increases so far.

"This is the longest freeze in two decades, and means fuel duty is currently 17 pence per litre lower than under previous plans - saving the typical motorist £9 each time they fill their tank. In total as a result, by the end of 2015-16 a typical motorist will have saved £673, a small business with a van £1,357, and haulier £20,717.”

Brent Crude is currently trading at US$29 a barrel, down from more than US$100 little over a year ago.

BP Group Chief Executive Bob Dudley told the BBC yesterday that a further fall to US$10 a barrel was “not impossible”.

Meanwhile, First Minister Nicola Sturgeon has called on Prime Minister David Cameron to sign an urgent city deal for Aberdeen to help it through the downturn.

The Scottish Government has offered to fund the deal on a 50:50 basis to support innovation, digital connectivity and infrastructure.

Edinburgh has overtaken the oil capital to become the most expensive city for renting a property in Scotland, with average rentals in the Granite City down by 15.9 per cent over the past year.