Tesco (LON:TSCO) is showing signs of continuing its recovery although arch-rival Sainsbury's (LON:SBRY) is catching up fast, according to latest data.
The beleaguered supermarket giant racked up its best sales figures since September last year, although they still fell 1.6% in the 12 weeks to January 31, figures from retail research group Kantar Worldpanel showed.
Tesco, which has wilted under the weight of an accounting controversy and competition from discounters, has launched a fightback under new chief executive Dave Lewis.
But Sainsbury's is still leading the quest for higher sales among the UK's established chains with a 0.6% rise in sales during the period, according to Kantar.
While Tesco is still the market leader with a share of 28.5%, that represented a fall of 0.5 percentage points against the 29% share it had a year ago.
But Sainsbury's leapfrogged over rival Asda into second place with a 0.1 percentage point rise to 16.8% , putting it ahead of the Walmart-owned retailer's 16.2%.
In the same period last year, Asda's market share was 16.9% against Sainsbury's 16.7%. Sales at Asda, which has been trying to claw back market share with another round of price cuts, fell 3.8%.
At Morrisons (LON:MRW), the sales decline lessened to 2.2%, while market share fell by 0.3 percentage points to 10.8%, leaving it in fourth place.
Elsewhere, there were signs that the explosive growth achieved by discount retailers Lidl and Aldi in the last few years was slowing down as the big four fought back.
Both accelerated their growth, with Lidl rising to 18.7% and Aldi to 13.7%, and their market shares by 0.7 percentage points, with Lidl’s rising to 4.2% and Aldi’s to 5.6%.
But both the latter figures were down from the 10% combined market-share high at the end of 2015.
The Co-op, meanwhile, became the fastest growing non-discounter for the first time since 2011, increasing sales by 1.4%.
Upmarket chain Waitrose, part of the employee-owned John Lewis Partnership, increased sales in the period by 0.1%, with market share flat at 5.2%.
The grocery market as a whole returned to slow growth after a disappointing Christmas period, increasing take-home sales by 0.2%.
Kanta's Fraser McKevitt said: "While the overall grocery market’s growth has been slight, New Year health kicks have contributed to a strong performance across fresh foods."