Four supermarkets have cut the cost of diesel to below £1 a litre – its lowest price for seven years.

Morrisons was first to drop its pump prices over the weekend, while Asda, Tesco and Sainsbury's followed suit today (Monday). Morrisons, Asda and Tesco are now charging 99.7p per litre of diesel. Sainsbury's is charging 99.9p.

The price of petrol, typically cheaper than diesel, fell below £1 a litre in the weeks before Christmas, but retailers were criticised for not passing on cheaper wholesale costs to diesel drivers.

Last month, the RAC urged supermarkets not to take advantage of motorists by charging more for diesel than they should.

With the wholesale price of diesel 3p a litre cheaper than unleaded, the RAC said retailers were in danger of being seen to take the country’s diesel drivers for a ride as there was no reason diesel should be priced higher than petrol.

"Diesel drivers will clearly welcome this move by the big supermarkets, although it would be fair to say it is overdue,” a spokesman for the RAC told the BBC.

"We hope that other supermarkets and the cheaper fuel retailers will follow suit and do the right thing for motorists. This should reduce the average price of diesel for motorists everywhere who will benefit from the low price of crude oil."

Oil is at its lowest for 11 years. UK Brent Crude oil is currently trading at just below $38 (£26) per barrel, having lost 35% over the year.

Connor Campbell, a senior market analyst at Spreadex, said: "It may have taken a while, but the dramatic drop in oil prices seen on the markets is finally beginning to filter through to customers.

"With unleaded petrol dipping below the £1 mark back in December, now diesel has joined its pump-peer, the big four supermarkets with Morrison’s taking the lead, pricing it under £1 for the first time since May 2009."

Diesel drivers filling up at one of the big four supermarkets will now pay £20 less to fill up a 50 litre fuel tank compared with the high point reached in 2012.

Freight Transport Association (FTA) deputy chief executive James Hookham said: “We need to see the wider fuel market become more responsive to ever lower oil prices.  Today’s announcement by leading supermarkets is good news for commercial vehicle operators.”

The FTA has long campaigned for a cut in fuel duty as a way help encourage growth in the economy, and backs the FairFuelUK campaign which has been spurred forward by the logistics industry, and since it was formed in 2011 has helped to secure a better deal for Britain’s hauliers and motorists.

Hookham concluded: “Never forget that at £1 per litre – 60p is fuel duty and about 16p will be VAT, so the biggest winner is the chancellor.  We need to see the Government helping businesses at these uncertain times with a further reduction in fuel duty in the Budget this March.”

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