Discounters are emerging as big winners in a slowing grocery market, TNS Worldpanel figures show.

The total market grew 4% year-on-year in the 12 weeks to 16 July compared with 6% in the 12 weeks to 17 June.

However, Lidl and Aldi bucked the trend, registering double-digit growth. Lidl's sales rose 13% while those at rival Aldi were up 11%. Each also achieved an increase in market share of 0.1 percentage points to 2.2% for Lidl and 2.6% for Aldi.

TNS attributed the growth to their ability to attract more shoppers as they continued aggressive store opening programmes.

Iceland also put in a strong performance, increasing its market share by 0.2 percentage points to 1.7% and growing sales 12% year-on-year.

Tesco, Asda and Sainsbury's sales all grew just ahead of the total market at 5%. Morrisons' sales rose 3%, while Somerfield's fell 6%. Tesco's market share remained static at 31.5%, Asda's rose from 16.6% to 16.7% and Sainsbury's grew from 16% to 16.2%. Morrisons' dropped 0.2 percentage points to take an 11.1% share of the market.

"The latest figures show the first signs of a consumer slowdown," said Chris Longbottom, research director at TNS. "This period compares with a buoyant period last year with the run up to the World Cup, and reflects the poorer weather this year combined with the increased squeeze on consumer spending,"

Nielsen figures published this week showed grocery sales growing at 4.8% year-on-year for the 12 weeks to 14 July. Tesco's sales grew 5.3%, Asda's and Sainsbury's 6.4% and Morrisons' 1.9%.