LONDON, July 23 (Reuters) - Sales fell at all of Britain's big four supermarket groups over the latest 12 week period, reflecting heatwave-boosted sales during the same period last year which made comparisons tough, industry data showed on Tuesday.
Market researcher Kantar said total grocery sales fell by 0.5% in the 12 weeks to July 14 - the first overall decline in the sector since June 2016.
It said sales at market leader Tesco fell 2.0%, while sales at Sainsbury's, Asda and Morrisons were down 2.3%, 2.0% and 2.6% respectively.
All of the big four lost market share to the German-owned discounters who continued to fare well. Aldi's sales were up 6.7% and Lidl's were up 7.0%. (Reporting by James Davey; editing by Kate Holton)