British motorists are being urged not to panic buy petrol as demonstrators begin protests at oil depots over high prices.Drivers fearing shortages have been buying up to a week’s worth of fuel in a single day to prevent being caught up in a repeat of protests which crippled much of the country five years ago. Yesterday, Britain’s Finance Minister Gordon Brown said the problem could only be addressed at a global level. “The first action we must take is to tackle the causes of this problem, ensuring concerted global action is taken to bring down oil prices and to stabilize oil markets for the long term,” he said. The cost of a litre of petrol climbed above one pound in some areas last week after the price of oil on world markets hit a record of more than 70-dollars a barrel. France meanwhile has warned oil companies that its ready to get tough over rising costs to cushion the blow to consumers. Three firms have already cut their prices but the government says the reduction is not enough.