Sales at Lidl grew by 13.9% in the 12 weeks to 10 July, while sales at Aldi were up 11.3%, according to research by Kantar, as more than two in three Brits shopped at either store at least once in the past three months. National supermarket sales nudged up 0.1% overall.
Grocery price inflation reached 9.9%, the second highest level since 2008, adding £454 to annual grocery bills.
Fraser McKevitt, head of retail and consumer insight at Kantar, said: “Grocery prices continue to soar to near record-breaking heights and have jumped by another 1.6 percentage points since last month.
“People will be feeling the pinch during our first restriction-free summer since 2019…[they] are increasingly turning to own-label products to drive down the cost of their weekly shop.”
The increased prices will be felt by shoppers this week as they line up to buy sun cream, paddling pools and burger buns to take advantage of the record summer heat.
The cost of a food shop for a typical family barbecue has risen more than 10% in the past year, Kantar data suggests, as the price of burgers went up 13% and the price of coleslaw rose 14%.
Sales of suncare products shot up 66% over the past four weeks, while sales of fans rocketed 107% last time the UK experienced a heatwave in July 2019.