The milk “price war” kicked off by Asda in the summer has boosted the big four’s volume sales and market share but very much at the expense of value sales, data ­released this week has revealed.

Sales volumes of pasteurised own-label milk across Tesco, Asda, Morrisons and Sainsbury’s stood at 184 million litres in the four weeks to 3 October [DairyCo Datum/Kantar Worldpanel], 5.2% higher than for the four weeks to 11 July.

The big four also increased their market share from 55% to 59% over the same period, as sales volumes across the major discounters and frozen-food specialists, including Aldi, Lidl, Iceland, Netto and Farm Foods, fell 12% from 48.67 million litres to 42.62 million litres. The discounters’ market share fell from 15% to 14%.

However, value sales slumped dramatically as a result. According to DairyCo, ­total revenues from the big four’s milk sales fell 8% between July and October after the price war brought the average price of one litre of milk down 12.1% to 58p per litre in October, compared with an average price of 66ppl in July.

The data showed the supermarkets had achieved what they had set out to do claw back their market share from the discounters, albeit at the expense of profitability, said David Swales, market intelligence manager at DairyCo. “Whether that’s a good or bad thing for them I guess depends on your viewpoint.”

Retailers probably saw the increase in milk market share as a success but might now start looking again at their profitability levels, he added.

At the end of July, Asda reduced the price of four-pint bottles of milk from £1.53 to £1.25, quickly followed by similar reductions from its big four rivals.

The move came after discounters and frozen food specialists had run cutthroat promotions on milk, selling four pints for £1. Jonathan Ovens, chairman of the Arla Foods Milk Partnership, said the price war, triggered by discounters, had removed £250m from the supply chain.