The AA has called on government ministers to launch an investigation into the regional pricing policies used by some of Britain's biggest supermarket chains.

The motoring organisation claims that motorists are being ripped off by a “postcode lottery”.

Edmund King, AA president, told Times Online prices charged by chains such as Tesco and J Sainsbury appeared to vary dramatically according to the level of local competition.

Tesco charges 106.9p per litre for unleaded fuel in Bury, Lancashire, but motorists in Waltham Abbey, London, are paying 7p per litre more.

J Sainsbury is charging motorists in Wembley 4p per litre more for unleaded than in Dundee.

Mr King said the AA feared the higher prices were being used to subsidise cheaper prices elsewhere. Tesco pledges to match the cheapest price in the local area.

The AA said that only towns with an Asda, which sets a national price, appeared to be getting a fair deal.

Mr King said: “Is it fair competition that one chain is charging a price in one town but charging 3p per litre more just down the road in another?

“Drivers ask does it really cost more for a tanker to deliver the same fuel to a town just a few miles down the road? A Mars Bar costs the same wherever you go, why shouldn’t fuel?”

He added: “It’s becoming a major issue and we are hearing from more and more MPs who have postbags that are bursting with letters from angry motorists.

“The government need to look at this and end what is little more than a post code lottery.”

The comments come only a week after Nigel Dodds, Northern Ireland’s finance minister, attacked supermarkets for failing to offer their cheapest prices to every customer.

Two months ago Tesco agreed to cut prices in Inverness after a local MP complained that its prices were 4p higher than in neighbouring Elgin.

A Tesco spokesman insisted the supermarket chain was a “force for good” for motorists. He added that it was far easier for Asda to offer a national price as it only has 170 forecourts across the country, less than half those run by Tesco.

He said: “Like most petrol retailers, we price match locally. I don’t think many people could argue that we are a force for good in petrol retailing and significantly cheaper than the oil companies.”

Petrol price have soared in the past year on the back of the high oil price.

Unleaded is currently averaging 110.6p, 16 per cent more than a year, meaning that motorists are spending an average of £7.60 more each time they fill up their car.

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