Sainsbury's share of the UK's grocery market now matches Asda, the country's second-largest retailer, according to the latest data from Kantar Worldpanel.

For the 12 weeks to 5 January, both Asda and Sainsbury's accounted for 17.1% of grocery retail sales in the UK.

The data showed Sainsbury's, which saw sales increase 3.1%, held its market share steady when compared to a year ago.

However, Asda's share of sales was down from the 17.5% record in the corresponding period last year after sales inched up 0.8%.

Sainsbury's was the only one of the UK's five largest grocers to hold their share of the market in the face of increasing sales at discounters including Aldi and Lidl at one end of the market and the continued growth at upmarket grocer Waitrose at the other.

Asda Tesco, Morrisons and The Co-operative Group all saw their share fall year-on-year.

Aldi, which accounts for 4% of the UK grocery market, saw sales increase 29.4%, boosted by new store openings but with sales outstripping its rivals. Sales at Lidl, which has a market share of 3.1%, were up 17.5%.