Asda has suffered eight months of falling sales despite a heatwave-fuelled spending boom across rival supermarkets.

The struggling grocer was the only major supermarket to report a decline in sales in the 12 weeks to Aug 9, with takings down 0.2pc on the same period last year.

It leaves Asda as the outlier among Britain’s major grocers, all of which enjoyed sales growth over the summer.

The fall in sales contrasted with growth of 1.8pc at Tesco, 3.5pc at Sainsbury’s and 3.3pc at Morrisons. Lidl was up 8.5pc, while Aldi grew sales by 1.1pc.

Asda, meanwhile, has yet to record sales growth this year, according to data from analysts at Worldpanel by Numerator.

Across the grocery market, sales rose 2.7pc as shoppers spent more on summer staples, including ice cream and sun cream.

Asda’s performance will pile pressure on Allan Leighton, its executive chairman, who returned to the supermarket in late 2024, promising to revive its fortunes.

There was some improvement, however. Asda recorded a market share of 11.9pc, up from 11.5pc in the same period a year earlier.

But it remains some way behind Tesco, which controls 27.8pc of grocery spending, followed by Sainsbury’s on 15.1pc. Aldi has 10.9pc, leaving Asda with only a narrow lead over its German discount rival.

It came as grocery price inflation slowed to 2.1pc, its lowest rate since October 2024, while shoppers increasingly turned to promotions to keep costs down.

Meanwhile, deals accounted for 31.3pc of sales in the latest month, the highest level this year.

Ocado was the fastest-growing grocer, with sales up 13.1pc, while Lidl gained the most market share, adding 0.5 percentage points to reach 8.8pc.

For Asda, the figures are the latest test of Mr Leighton’s attempt to turn around the supermarket.

The business plunged to a loss of almost £1bn last year after sales fell 3.4pc, while its debt interest bill climbed to £730m.

Mr Leighton has sought to win back customers with aggressive price cuts, warning that the strategy would result in a “material hit” to profits.

Despite those efforts, Asda’s market share has remained under pressure since its £6.8bn takeover by private equity firm TDR Capital and the Issa brothers in 2021.

Its share have fallen from around 14.3pc at the time of the takeover to 11.9pc on Monday.

Asda was approached for comment.