The head of the UK’s second-largest supermarket chain has warned of further pain to come as rampant inflation continues to devour consumers’ spending power.

Sainsbury’s chief executive Simon Roberts said the pressure on household budgets “will only intensify over the remainder of the year” as the retail group, which also owns the Argos and Habitat chains, revealed a 4 per cent decline in overall sales during the 16 weeks to June 25. The figures emerged as shoppers switch to cheaper products such as frozen food, tinned goods and own-label items, with sales of “big ticket” items such as electronics on the decline.

Sainsbury’s said sales of its cheapest own-label products were up by more than 5% in the first quarter of its financial year as shoppers attempt to offset rising prices by switching away from big brands. Under the group’s Aldi price match campaign, Sainsbury’s is currently duplicating its discounting rival on more than 240 products.

Mr Roberts, who took over the top job in 2020, said Sainsbury’s is doing “everything we can” to keep prices low and will invest a further £500 million to do so.

“We’re working hard to reduce costs right across the business so that we can keep investing in these areas that customers care about most,” he said. “The progress we are making on improving value, quality, innovation and service is reflected in our improved grocery volume market share.”

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Grocery sales were down 2.4% against the same period a year earlier when revenues among “essential” retailers were boosted by Covid lockdowns. Compared to the same period prior to the pandemic, sales were 8.7% higher.

General merchandise was down 11.2% on a year earlier, but the sales trend “improved” after the first five weeks of the first quarter when comparisons suffered against the previous year’s lack of competition from non-food retailers who were forced to close.

Sales at Argos were down 19% in the first five weeks, but that eased to a decline of 7% in the final 11 weeks. General merchandise sales at Sainsbury’s were 30% lower in the first five weeks, improving to a fall of 5% in the final 11 weeks.

Clothing sales were 10.1% lower during the first quarter following 26% decline in the first five weeks. That improved to a 2% decline in the last 11 weeks.

Mr Roberts noted that shoppers are “watching every penny and every pound” yet still proved willing to spend on treats for special occasions such as the platinum jubilee, when sales of its premium Taste the Difference ranges were up by 12%.

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Matt Britzman, equity analyst at Hargreaves Lansdown, said jubilee celebrations may have provided consumers with a temporary distraction but it’s now “very much back to reality”. While cost-cutting has allowed Sainsbury’s to raise prices at a slower pace than its competitors, there is a “limit as to how much fat can be trimmed”.

“It doesn’t come as much of a surprise that management are warning of a consumer that’s watching every penny as the cost-of-living crisis takes its toll, and the group’s expecting that pain to only get [worse],” Mr Britzman said.

“It’s positive then to see guidance remain intact, though it’s worth remembering it’s been raised and lowered already this year.”

Shares in Sainsbury’s closed yesterday’s trading 2.2p higher at 210.6p.