From today Asda, Tesco and Sainsbury's are cutting petrol prices by up to 2p a litre, with diesel being reduced by 1p.
At Asda this will take the price of its petrol to no more than 124.7p a litre, with diesel 128.7p - its lowest prices since January 2011.
The AA said the average UK price of petrol yesterday was 129.71p a litre, with diesel at 133.74p, the lowest since mid-February 2011.
Paul Watters of the AA said the supermarkets' move would spur other retailers to follow suit.
RAC fuel spokesman Pete Williams said: "We've been calling for petrol and diesel prices to fall for some time following the decrease in wholesale prices and so this is a welcome move by the supermarkets.
"We would expect to see other retailers to follow in the coming days."