All big four supermarkets saw sales fall again in June as the grocery market overall declined for the first time since January.
Kantar Worldpanel, which compiled the data, did have some comfort for the majors as it suggested Brexit uncertainty would not hit sales to any great degree.
“While these latest figures pre-date the EU referendum result, the immediate economic uncertainty is unlikely to cause a substantial fall in grocery volumes, as demonstrated by the 2008 financial crisis when basic food, drinks and household sales proved resilient,” said Fraser McKevitt, head of retail and consumer insight at Kantar.
Discounters Lidl and Aldi increased their market shares, which now stand at a combined 10.5% or the highest on record. Lidl increased sales by 13.8% and Aldi by 11.5% on a year ago.
Other rivals to the big four also picked up, with the Co-op's sales 2% higher and Waitrose up by 1.3% thanks to its premium Waitrose 1 brand.
It was a different story for Tesco (LON:TSCO) , Sainsbury’s, Asda and Morrisons, however.
Asda saw sales tumble by 5.9% in June, Morrisons by 2.4% while Sainsburys and Tesco were 1.4% and 1.3% lower respectively. The big four still dominate the market, nonetheless, with a combined market share of almost 71%.
Total grocery sales fell by 0.2% in the three months to 12 June as like-for-like prices declined by 1.4% on a year ago.