He has launched his campaign in a week when the AA said motorists are paying 9p a litre too much for petrol because garages are failing to pass on the full cut in oil prices.

Mr Opik has written to the Chief Executive of Morrisons, urging them to adopt a common price policy to ensure petrol prices in rural branches are the same as in the rest of their stores.

A cut of two pence per litre to unleaded petrol and four pence to diesel has left the price in most Morrisons at 111.9 pence and 122.9 pence respectively, yet at Morrisons' in Newtown branch unleaded is priced 112.9 pence and diesel at 125.9 pence.

Some supermarkets operate a common price policy which means that fuel is the same price at each of their branches.

Lembit Opik, Montgomeryshire's Welsh Liberal Democrat MP, has been campaigning to cut fuel prices, and has called for a rebate on fuel duty in rural and remote areas to eliminate the disparity between petrol prices in urban and rural areas.

"I am disappointed, but not surprised, to see that Morrisons' petrol in Newtown is more expensive than their petrol elsewhere in the country, and I have written to the Chief Executive asking them to urgently look into the situation.

"I appreciate that there are extra costs in transporting fuel to areas that are more remote, but given the extraordinary cost of petrol at the moment I would hope that supermarkets that operate differential price policies would recognise that rural communities don't deserve to be penalised.

"Rural areas are being hit hard by higher prices across the board, and the recent increase in fuel prices has been particularly damaging for people in sparsley-populated areas who have no choice but to use a car.

"I welcome the recent price cuts that should ease the burden on families in rural communities, but I don't see why those in rural areas shouldn't receive the full benefit.

"If the Government agreed to Liberal Democrat calls for a rural rebate on fuel duty this wouldn't be an issue as it would take out a lot of the extra costs that fuel retailers face in rural areas and hence reduce the gap in prices at the pump, but at the moment Labour seem more interested in internal squabbling than in helping ordinary people."

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