Aldi has become the latest grocery chain to pledge a new minimum price to farmers for milk sold in its stores.
It said it will pay at least 28p per litre from next Monday following talks with the National Farmers' Union (NFU).
The announcement follows numerous demonstrations against supermarket chains over the past few weeks, with farmers calling for a fairer price for the dairy industry.
A spokesman for Sainsbury's said its milk prices were already competitive: "Our dairy group farmers benefit from a cost of production model - this sets a price that directly reflects their costs on the farm, building in a profit, as well as rewarding outstanding animal welfare and environmental standards."
Asda already announced that it is increasing the price it pays its milk supplier to "a level that will assist" farmers. Asda will commit to paying 28p per litre for 100% of its liquid milk volume throughout its entire range.
NFU president Meurig Raymond said: "The NFU has been lobbying tirelessly for Asda to recognise the plight of the dairy industry so we are pleased that Asda has moved to support farmers in their hour of need."
Tesco has so far ruled out a similar move, saying that it pays a fair price based on the cost of production.