"Shrinkflation" - where pack sizes and portions reduce but prices remain the same - means shoppers are returning to the supermarket more often, as what they're buying simply doesn't last as long.
Consumers' Association of Ireland chief Dermott Jewell said: "Many people are going to the supermarket once or twice a week, and one of the reasons is they're getting less for the money that they're paying - that's the shrinkflation element."
He added: "People are buying the same things on paper but they're not lasting as long they're not as big - it's that simple.
"I don't see where they can save much more. They've moved to the own-brands, they've moved in every way they can, they've expanded on their cooking to make meals last days and freeze them, they've run out of options."
In the four weeks to January 23, the average price per pack rose 14.6%, while the volume of shopping per trip was down 13%, showing the challenges shoppers face, according to the latest data from retail analysts Kantar.
In Association with
And in the 12 weeks to January 23, shoppers spent an extra €90.50 per household year-on-year. The inflation rate of 16.3% is the highest since Kantar started tracking grocery sales back in 1948.
Kantar senior retail analyst Emer Healy said: "The sector growth comes as grocery price inflation hit 16.3%. However, this does trail just behind Great Britain where inflation hit 16.7% after two months of slight decline."
She said Irish households will now face an extra €1,159 on their annual shopping bills - more than €96 a month - if they "don't change their behaviour to cut costs".
Ms Healy added: "It's no surprise that shoppers continued to trade down to supermarkets' own-label products this period, with sales rising 10.4%, well ahead of a 4.7% increase in branded lines".
Sales of premium own-label goods topped €152.6m in the 12-week period, up €5.7m year-on-year, with €26.7m of that coming from premium own-label chilled convenience products - a strong growth of 11.6%.
However 'value' own-label goods saw the strongest growth, up 34% year-on-year with shoppers spending €17.9m more on these ranges.
Despite the price rises, the grocery market is more competitive than ever, with shoppers looking for the best deals and retailers looking to retain customers, Kantar said.
"This is reflected by many supermarkets using their loyalty schemes to help shoppers save," it added.
Nearly 40% of shoppers claim to always use a money-saving voucher, Kantar found.
Retail Excellence chief Duncan Graham said: "Grocery retailers are aware of the impact that inflation is having, particularly at this time of the year."
