Milk buyers announced another rash of major price increases for dairy farmers this week, putting pressure on Tesco and Sainsbury's to follow suit.

The two retailers have set up segregated milk supplies and determine the price for farmers supplying them, but those prices have been left in the shade by increases of up to 5ppl by other milk buyers.

"Sainsbury's is under pressure now because one of its suppliers, Dairy Crest, has committed to 25ppl from October," said Tom Hind, NFU chief dairy adviser. "They will have to respond to that."

Sainsbury's currently pays about 20.5ppl. Tesco is now reviewing its 22ppl rate and industry observers expect a rise of at least 4ppl.

"They'd probably want to be the top payer from the prestige point of view," Hind added.

Meanwhile, Asda will start to pay 26ppl for milk in October and Marks & Spencer has upped its standard litre price by 2.67ppl to 24.73ppl.