Both supermarkets have been losing customers to discounters such as Aldi and Lidl as price pressures grow.

Asda announced it had “dropped and locked in” prices on some products until the end of the year.

Meanwhile, Morrisons said it would offer an average 13% price cut on more than 500 goods including eggs, beef and rice.

Asda said more than 100 products covered by its “dropped and locked” promise ranged from some fresh fruit and vegetables to fresh meat and frozen food. The supermarket said prices would drop by 12% on average.

“We know that household budgets are being squeezed by an increasing cost of living and we are committed to doing everything we can to support our customers, colleagues and communities in these exceptionally tough times,” said Mohsin Issa, co-owner of Asda.

Last month, Asda launched its Just Essentials range promising an expanded line of low-cost products in all its stores from May.

Last week, the UK’s largest supermarket chain, Tesco, said its profits last year more than trebled, but said its performance this year would be affected by the need to keep prices down.

Both Asda and Morrisons are losing out as customers turn to discounters Aldi and Lidl, to cut their costs, according to research firm Kantar.

UK grocery price inflation hit 5.2% in the 12 weeks to 20 March, it said, its highest level since April 2012.

In that time, Lidl and Aldi were the only big supermarkets to see their sales and market shares rise. By contrast, Morrisons and Asda saw the biggest drops in sales and market share.

Kantar’s head of retail Fraser McKevitt said: “We’re really starting to see the switch from the pandemic being the dominant factor driving our shopping behaviour towards the growing impact of inflation, as the cost of living becomes the bigger issue on consumers’ minds.