Sainsbury is still holding onto second place in our TradeTrak survey, despite the latest TNS Superpanel data showing that Asda has overtaken JS and secured second place for the first time in the four weeks to July 20.

The disparity is explained in the different ways the two sets of data are measured.

TradeTrak, compiled by ACNielsen, is based on all grocery purchases brought into the home. Grocery is defined as food, household, confectionery, petcare, liquor and toiletries.

In contrast, the TNS Superpanel data measures all trading at the till, excluding petrol and instore concessions.

Both sets of data prove that it is Asda’s strength in non-food that is paying off for the Wal-Mart owned retailer.

Electricals and clothing - in particular the successful George range - account for much of Asda’s growth and it is this that has taken the company into second place in the TNS Total Till Roll figures.

Sainsbury remains predominantly a food retailer, although it is pushing harder into non-food this autumn.

Its share of traditional grocery expenditure is 15.5% in the last quarter according to TradeTrack, compared to Asda’s 13.9%.

While Sainsbury and Asda tussle it out to hold the coveted number two spot, Tesco appears to be the main winner. It is up 0.7% in market share year on year according to the ACNielsen data.

The UK’s number one retailer commanded a 23.4% share of trade expenditure for the 12 weeks to July 12. According to TNS, Tesco enjoys a 27% market share overall.

Safeway last month said that its like-for-like sales were down 0.6% for its first quarter.

Its market share as recorded by TradeTrak was up marginally on the previous quarter at 9.1%, but was down year-on-year.