Asda supermarket petrol prices will fall by 1p to 105.9p and diesel by 2p to 116.9p at its 170-plus stations across the UK from Tuesday.
Morrisons said it is cutting prices by the same amount - to 106.6p and 117.0 - at all its 285 forecourts across the UK from 6pm on Monday night.
Total UK had said it would drop its prices over the weekend by at least the same amounts, although it did not specify what the new prices would be.
And a spokeswoman for Shell said: "Earlier this week we reduced our prices by 1p or 2p a litre at company-owned petrol stations."
AA spokesman Luke Bosdet said: "Although very welcome in bringing the cost of a tank of petrol down by 50p, many non-Asda towns will still be charging 3p a litre more next week.
"This turns buying fuel in the UK into a postcode lottery where drivers in one town can be spending £1.50 a tank more than another just down the road."
Asda trading director Darren Blackhurst said: "We urge our rivals not to take advantage of drivers who don't live close to an Asda petrol station and to pass on cost benefits fairly."
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