TNS puts Sainsbury's market share at 15.9 per cent, close behind Asda's 16.6 per cent.
TNS Superpanel director Peter East said that the narrowing of the field showed that Sainsbury's recovery appears invigorated as it strives to address well-publicised price competition and availability issues and 'indicated an intensifying battle between leading grocery retailers for market share'.
A spokeswoman from Sainsbury's said: 'It is pleasing to see independent measures reflecting our efforts and it is evidence of the early shoots of recovery we reported at Q4. We are pleased with our progress to date, although we remain realistic about the task in hand.'
However, neither of the two retailers come anywhere near Tesco's dominance of the market. Its market share is almost as much as Sainsbury's and Asda combined, at 29.5 per cent. It grew over the period by 11 per cent year on year.
For the latest on Tesco's supermarket dominance see this Friday's Retail Week.