BELEAGUERED motorists could be forgiven for assuming that every time they fill up their tanks they will pay more and more.

After all, fuel prices have seen a steady rise during the last few years - with month-on-month increases becoming the norm.

It's no surprise The Association of British Drivers recommends people shop around for the best deal before going to the pump.

Judging by the differences in price for a litre of diesel and a litre of unleaded petrol across the region's service stations it's easy to see why.

In an ever-changing market one of the cheapest service stations for both petrol and diesel is Asda in Bournemouth Road, Chandler's Ford, with unleaded currently 111.9p per litre and diesel 121.9p.

However, at the bottom of the service station league table is Woolston Shell Service Station in Portsmouth Road, Southampton, for having the most expensive unleaded priced at 116.9p a litre.

Meanwhile, the most expensive place to buy a litre of diesel is at the Texaco Queensway Service Station in Queensway at a cost of 130.9p per litre.

Neither managers of the two stations wished to comment when approached by The Daily Echo about their prices.

Unsurprisingly an Asda spokesman was more than happy to say that Asda supermarket did its best in "times of belttightening and price rises" to be the best value option.

However, petrol pricing expert Louise Doherty warns against assuming that supermarkets are always the best option.

"There is an assumption that supermarkets are always cheaper but this is not necessarily the case.

"The main thing that will affect the price of petrol on a station forecourt is the local competition.

"Generally petrol stations on motorways are more expensive, and so are petrol stations in more affluent areas.

"There is more chance of finding cheaper prices in less affluent areas - but it always depends in the end on local competition."

Nationally last month motorists saw the highest month-on-month rise in the cost of diesel with the price rocketing by 6.7p a litre so the average price is now 124.17p.

Meanwhile the average price of unleaded petrol shot up by 4.49p to an average price of 112.55p a litre.

According to an AA survey , supermarkets were 2.5p a litre cheaper for petrol and 4p less expensive for diesel - but there are wide local variations.

Nigel Humphries, The Association of British Driver's Regional spokesman said: "Motorists should shop around and try to get the lowest price possible.

"Prices can change and it's important to stay alert and make notes of good deals on the forecourts.

"Wherever possible motorists should avoid filling up their tanks at motorway service stations."

He said the level of fuel duty coupled with an increasing demand for fuel from China and India and market speculators overpricing oil are all factors contributing to the increases.

But Mr Humprhies said that motorists could save money by making their car as fuel efficient as possible by not driving around with unnecessary weight, ensuring tyre pressure is correct, removing roof racks and turning off air conditioning.

Cheap petrol?: Do you know a place where you can fill up cheaply.

Contact Clare Kennedy on 023 8042 4500 or email clare.kennedy@dailyecho.co.uk co.uk