Waitrose and Aldi have built on their record share of the grocery market as shopping habits continue to be driven by "austerity and provenance".
The latest Kantar Worldpanel figures for the 12 weeks to March 17 show further market polarisation, with Waitrose growing sales by 12.5% and extending its market share to 4.8%, from 4.4% a year earlier.
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Budget chain Aldi's sales were up 30.8%, boosting its share from 2.6% a year ago to 3.3%. Tesco is still the market leader, although lacklustre growth of 1.1% means its market position is down to 29.4% from 30.2% in the same period of 2012.
Sainsbury's is the clear winner among the big four supermarkets, with year-on-year growth of 6.2% ahead of total market growth of 3.9%, taking its share to 16.9% from 16.6%.
The figures cover a period of low wage growth and rising inflation and as shoppers grapple with the fall-out from the industry's horse meat scandal.
Fraser McKevitt, retail analyst at Kantar Worldpanel, said: "Austerity and provenance are the key factors behind the varying retailer performances this month.
"Continued pressure on household budgets has helped Aldi, Lidl and Iceland to record market-beating growths while Waitrose and Sainsbury's have managed to mostly avoid adverse media coverage from the horse meat scandal."
Lidl's sales grew by 10.5% in the period, taking its market share to 2.9%, while Iceland grew by 8.7%, with a market share of 2.1%.