Petrol retailer Shell has warned continued strike action by tanker drivers will have a "significant impact" on its forecourts.

The firm said around 15 per cent of its petrol stations have been disrupted by the walkout, and that demand has been "high but not extreme".

A spokeswoman said: "Sales remain high but are not at extreme levels, and there are still few signs of panic buying.

"As the strike continues, it is inevitable that in time, there will be a significant impact on our petrol stations."

Demand for fuel has been high since talks to avert a four-day walkout by Shell tanker drivers broke down on Thursday.

The Petrol Retailers Association reported a 25 per cent increase in sales across the industry over the past week.

BP said while sales were high on Friday, Saturday trade was normal.

A spokeswoman added: "We've got a well-rehearsed contingency plan in place and we're monitoring the situation on a daily basis."

Website PetrolPrices.com has warned up to 54 parts of the country could be left without fuel during the strike action.

It said 19 areas have one Shell petrol station within a five-mile radius and no alternative, and 35 areas have just one alternative.

Supermarkets said they were working to maintain supplies in the face of increased sales.

A Tesco spokesman said: "Tesco is experienced in coping with these types of situations and we've worked hard to keep pumps supplied and open.

"In some cases people have seen the media reports predicting shortages and they've changed their normal buying habits, emptying pumps faster than we can fill them. There is petrol coming through and any outstocks have been short-lived."

A spokeswoman for Morrisons said their petrol stations have seen high demand over the past week and additional deliveries are being made to their forecourts.

She added: "To reduce the risk of shortages and unnecessary queuing we would ask that people are sensible when purchasing their fuel."

The Shell tanker drivers walked out in a pay row with haulage companies Hoyer and Suckling.

Members of the Unite union began a four-day walkout on Friday, and have warned they will strike again next weekend unless the dispute is resolved.

They say drivers are on a basic salary of £31,800, and if their jobs had not been outsourced from Shell they would now be earning £46,000.

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