Prime Minister Andy Burnham is right to challenge fake "was" prices and invented reductions, according to Aldi UK chief executive Giles Hurley.
Hurley said supermarkets should compete on the total price of a weekly shop rather than the size of discounts offered through loyalty schemes.
Most major full-price supermarkets now run loyalty programmes, offering lower prices on selected products to members while those without the right card or app pay more.
The Competition and Markets Authority found in 2024 that 92 per cent of loyalty-priced products offered a genuine reduction against a retailer's usual price.
Loyalty card costs
However, Hurley said a genuine discount can still leave the final price expensive, arguing that a loyalty badge is not proof shoppers are getting the best value.
In July, the consumer group Which? priced a list of 93 everyday grocery and household items across eight supermarkets, taking loyalty discounts into account.
The average total at Aldi was £158.05, making it the UK's cheapest supermarket for the ninth consecutive month.
The same list cost £187.86 at Sainsbury's with Nectar prices and £188.45 at Tesco with Clubcard prices, meaning shoppers would have paid about £30 more.
"A spectacular saving on one product can feel rewarding," Hurley said. "But families don't pay their grocery bills one product at a time. What ultimately matters is the total at the checkout."
Everyday pricing
Aldi operates an everyday low pricing model designed to make a core grocery shop affordable from the outset, where the same price is available to every customer.
Consumer groups have warned that millions of people can be excluded from loyalty prices because of age, address requirements or limited digital access.
Which? reported this spring that one in ten UK households was skipping meals to keep costs down, with 85 per cent of adults worried about food prices.
"Against that backdrop, all supermarkets have a duty to do everything they can to keep prices as low as possible," Hurley said.
He added that grocery prices can change as the cost of ingredients, energy, transport and labour changes, but that the overall pricing philosophy should remain constant.
Hurley said the government's consultation on pricing should be rigorous and targeted, and that swift action must be taken against deceptive practices.
