Asda has seen sales fall 5.8% during the three months that include Christmas - its biggest quarterly sales fall on record.
The chain, which is owned by US retailing giant Walmart, saw sales fall 4.7% over the year as a whole.
The sixth consecutive quarter of declining sales confirms Asda endured the worst sales performance of all the major grocers over Christmas, as it lost out to discounters Aldi and Lidl as well as major rivals Tesco, Morrisons and Sainsbury’s.
Chief executive Andy Clarke, who previously described the 4.7% sales slide as a “nadir” for Asda, admitted that the supermarket’s sales performance had been worse than expected.
He insisted Asda had enjoyed a successful Christmas because it had met its strategic objectives in reducing discounting, keeping profits stable and selling out its seasonal products.