The big four grocers are competing over an “ever-smaller middle ground” as Aldi, Lidl and Waitrose steal market share from larger rivals at the discount and premium ends of the market, Kantar Worldpanel reports.

Aldi enjoyed record sales growth of 32.7% year on year over the 12 weeks to September 15. Lidl and Waitrose also performed well with respective growth rates of 14.3% and 9.7%.

Sainsbury’s recorded 5.1% sales growth over the period, Asda 2.4%, Tesco 1.9% and Morrisons 1.6%. The Co-op’s sales grew 0.3% and Iceland’s 4%.

Kantar reported that Aldi, Lidl and Waitrose had taken three grocery market share percentage points from larger rivals over the last three years.

Waitrose now has a market share of 4.9%, Aldi 3.7% and Lidl 3%.

The UK’s largest grocer Tesco’s market share was 30.2% in the 12-week period, down from 30.9% last year. Asda’s fell to 17.3% from 17.6% last year, while Morrisons’ fell to 11.1% from 11.4%.

Sainsbury’s was the only one of the big four to grow market share, up to 16.6% from 16.4% last year.

Kantar Worldpanel director Ed Garner said: “The discounters have continued to perform strongly with year-on-year sales growth of 32.7% for Aldi, another all-time record, and 14.3% for Lidl. At the same time there is no sign of Waitrose running out of steam as it delivers growth of 9.7%.

“Strong performances by retailers at both ends of the market pose a significant challenge for the big four supermarkets. The combined growth of Lidl, Aldi and Waitrose has taken three market share points [from larger retailers] over the past three years and is forcing the major supermarkets to compete for an ever-smaller middle ground.”

He added: “Price-match promotions such as Asda’s Price Guarantee, Sainsbury’s Brand Match and Tesco’s Price Promise have meant that price is less of a differentiator and shoppers cannot be convinced to switch outlets based on cost alone.”

Kantar said premium own-label lines are performing strongly with Tesco Finest and Sainsbury’s Taste the Difference enjoying double-digit sales growth.