Supermarket giants Asda and Morrisons have reduced the price of unleaded fuel to 99.9p a litre, the first time since December that the fuel has cost under £1.
At its peak price this summer a litre of petrol retailed at more than 120p.
The drop in price reflects the falling cost of oil, which now stands at $80 a barrel from a summer high of $147, and a battle between the supermarkets to attract customers in the current economic climate.
BP has also reduced unleaded fuel prices to just under a pound at selected forecourts.