Sainsbury's has followed its rival Tesco in cutting the price of its milk.
But unlike Tesco - who said it made the move because its costs for buying in milk had fallen - Sainsbury's did not give a reason for its decision.
Both supermarkets regularly battle on food prices and face stiff competition from discounters Aldi and Lidl.
The move from Sainsbury's and Tesco comes at a time when food inflation is at its highest level since 1978 and latest figures show that food prices increased 18.2% from February 2022 to February this year.
Milk alone has risen by 43% in price over the same period, one of many staples, including cheese and eggs, which have surged in cost and squeezed household budgets.
But some analysts have suggested that supermarkets reducing their prices is a possible sign that hikes in the cost of a weekly shop could be starting to ease.
Everyday essentials
Sainsbury's said with "costs going up, we are working hard to keep prices low, especially on the everyday essentials people buy the most".
A spokesperson told the BBC: "Our customers can be confident that they will receive great deals when they shop with us, and do not need to go anywhere else to get the best prices on their weekly shop."
Both supermarkets said the reductions in price will not affect how much they pay farmers.
Meanwhile, Asda has announced a shake-up to its reduced items on sale.
Following a trial in 140 stores, Asda said it would now have price cuts on products twice a day, rather than three times previously, but that the markdowns would be greater than before.
Recent research has revealed nine out of 10 shoppers reported feeling concerned about rising food prices, according to Barclays. Around 62% said they were finding ways to reduce the cost of their weekly shop, a report showed.
Swapping fresh for frozen
Consumers are swapping from fresh to frozen food to save money. Frozen food is outperforming fresh in supermarkets at the moment, data from research firm Kantar suggests.
Frozen chicken, ready meals, pizzas and chips are the most popular items.
FTSE 100
The UK's top share index, the FTSE 100, was up nine points at 7,853 shortly after opening this morning, following yesterday's 18-point gain.
Brent crude futures were 0.16% higher at $86.23 a barrel.
Companies reporting today
- Trading update: Hays, 888 Holdings