Kantar, formerly TNS Worldpanel, said yesterday that overall UK grocery sales rose 3.7 per cent year-on-year in the 12 weeks to 13 June, including food price inflation of 1.5 per cent.
Among the top four supermarket groups, Morrisons saw the fastest growth, with sales up 6.1 per cent.
It was followed by Sainsbury's on 4.4 per cent, sector leader Tesco on 3.7 per cent and Asda on 2.7 per cent.
Part of Asda's recent underperformance is because it has been opening fewer new stores than its rivals.
Waitrose, which has been expanding rapidly, saw sales growth of 11.2 per cent.