Three of the UK’s major supermarkets have cut petrol prices to below £1 a litre following the collapse in the global oil market.

Morrisons, Asda and Tesco all announced that the cost of unleaded petrol would fall to less than £1 a litre, the first time it has been available nationally at that price for four years. The moves were the latest in a string of price cuts that began in March.

On Monday morning Morrisons announced that with immediate effect motorists using its filling stations would pay a maximum of 99.7p a litre for petrol and no more than 104.7p a litre for diesel.

Asda quickly followed suit, cutting its prices to the same level, in a move it said would “support the nation during these unprecedented times” and lower the cost for those returning to work or completing essential journeys.

Tesco, the UK’s biggest petrol retailer, said that on Tuesday it would be cutting the cost of unleaded petrol to no more than 99.9p a litre and 105.9p on diesel at its 500 outlets.

Global oil prices have plunged since the start of the year to 21-year lows as a result of a standoff over production levels between Saudi Arabia and Russia and a sharp slump in demand for crude and transport fuels due to coronavirus lockdowns. The price of a barrel of Brent crude, the global oil benchmark, has crashed from nearly $70 at the turn of the year to less than $30. At one point it stood at $18.

Simon Williams, a fuel spokesman for the RAC motoring group, said the initial move by Morrisons had brought petrol and diesel to “a very fair price and one that is much more reflective of what the retailer is itself paying to buy the fuel in”.

However, he said the low price may not last long. “It remains to be seen how long prices this low will persist for, with some early indications that wholesale petrol prices have started to rise as a result of the world oil price creeping up.”

Oil traders are betting that market prices will rise in the second half of the year as the US and Chinese economies reopen in the months ahead. At the same time, the world’s largest oil producers are now cutting back production to help ease the oversupply in the market.

Williams said that there was “a darker side” to any large cuts to pump prices as “they heap yet more pressure on smaller independent fuel retailers, who in some cases are already fighting for survival as a result of the coronavirus outbreak”.