Grocery price inflation in the UK has soared to a record 14.7%, driving up the average supermarket bill by £682 per year.
Just over a quarter of households (27%) say they are struggling financially — double the figure recorded last November, the research firm said.
Own label sales jumped by 10.3% over the last four weeks, as shoppers manage their budgets while the branded goods market grew far more slowly at 0.4%.
Prices are rising fastest for items such as margarine, milk and dog food.
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Aldi was the fastest growing retailer in the latest period, increasing its sales by 22.7% year on year to gain 9.2% market share, while Lidl boosted sales by 21.5% to take its market share to a new record of 7.2%.
Asda again led the traditional "Big Four" supermarkets with sales growing by 5.3% to maintain an overall market share of 14.3%.
Researchers said that there is currently "no peak in sight" in terms of grocery price inflation, meaning a new record high could be set as food prices continue to rise.
Fraser McKevitt, head of retail and consumer insight at Kantar, said: “Yet again, we have a new record high figure for grocery price inflation and it's too early right now to call the top.
"Consumers face a £682 jump in their annual grocery bill if they continue to buy the same items and just over a quarter of all households now say they’re struggling financially, which is double the proportion we recorded last November.
"Nine in 10 of this group say higher food and drink prices are a major concern, second only to energy bills, so it’s clear just how much grocery inflation is hitting people’s wallets and adding to their domestic worries.”
Fewer people stocked the cupboards for Christmas in October, preferring to wait until later in the year.
McKevitt said: “This time last year 2 million consumers had already bought their festive Christmas pudding. We’ve seen 32% fewer shoppers doing that this time around, suggesting people are not trying to spread the cost of their purchasing — at least not in October.”
Fewer households also bought pumpkins last month compared to last year, Kantar said.
Sue Davies, head of food policy at consumer group Which?, said: “The rocketing price of food is a real concern with millions of people skipping meals or struggling to put healthy meals on the table.”
“It is essential that households get the support they need from the government and businesses amid the cost of living crisis.”
“Supermarkets must ensure budget lines for healthy and affordable essential items are widely available across their stores.”
“Promotions should be targeted at those most in need and people supported so they can easily compare the price of products to get the best value.”