Tesco had the smallest drop in sales of the big four, at 0.1 per cent, and Asda the biggest, with a 5.1 per cent decline in sales.
Discounters Aldi and Lidl both showed double-digit sales growth, at 11.4 per cent and 14.2 per cent respectively.
At the other end of the scale, Waitrose posted a 2.1 per cent growth in its sales, performing well at the high end of the market. The supermarket achieved a 5.3 per cent share of the grocery market, which is a record for the retailer.
Edward Garner, director at Kantar Worldpanel, said: "While the big four are struggling to keep their market share what’s clear is that consumers aren’t flocking away from their stores – their combined shopper numbers have dropped only 0.2 per cent in the latest 12 weeks. In fact, 94 per cent of Aldi and Lidl shoppers still visit at least one of the four major retailers every four weeks.
"However, consumers’ spend is increasingly being shared with other growing outlets which also include Waitrose, the Co-operative and Iceland and average household spend for the big four has dropped by 2.9 per cent.
"Asda’s low-price positioning continues to feel the targeted effect of Aldi and Lidl’s growth – sales fell 5.1 per cent on last year giving it a 15.8 per cent share of the market."
Jonathan Neale, joint managing director of buying at Aldi, said: "The price gap between Aldi and other supermarkets is bigger than ever.
"Not only are we the cheapest, Aldi brands are being judged as the best quality, too...our customers know that they don't have to pay high prices to get the best quality groceries."