The average price of unleaded petrol in the UK has passed a pound a litre for the first time. The car research group Catalist puts the cost of unleaded petrol at a pound and point eight of a penny. The average price of a litre of diesel is one pound 3.32 pence. Supply concerns and the weak dollar have pushed up oil prices globally but the UK tax for petrol and diesel was also increased by 2p a litre from the start of October.