J Sainsbury (JSAIY)   rose to the top of the FTSE 100 leaderboard Wednesday after the U.K.'s second-largest supermarket posted better-than-expected sales for the third quarter as U.K. retailers continue to defy concerns of a slowdown in spending following the country's decision to leave the European Union last June.

Sainbury's shares surged more than 6.41% in the opening 45 minutes of London trading to change hands at an eight-month high of 2758 pence each, extending their three month gain past 16% against a 0.47% decline for the FTSE 350 Retailers Index.

Sainsbury's, the U.K.'s second-largest supermarket chain, said total retail sales, excluding fuel, rose 0.8% in the three months ending on Jan. 7, while like-for-like sales rose 0.1% against an analysts' consensus of a 0.8% decline. Sales at its Argos discount retail brand rose 4.1% over the period and 4% on a like-for-like basis, Sainsbury's said.

"Sainsbury's offered customers greater quality food, choice and value than ever before, across all channels. We had a record Christmas week, with over 30 million customer transactions at Sainsbury's and over £1 billion of sales across the Group." said CEO Mike Coupe. "Thanks to the commitment of all our colleagues, we delivered an excellent shopping experience and helped our customers live well for less over the festive period."

"Our Groceries Online and Convenience channels performed well, achieving over nine and six per cent sales growth respectively and at Argos we saw record levels of online participation. Online sales made up 18 per cent of total Group sales in the quarter," Coupe added. 

Sainsbury's figures follow a better-than-expected Christmas season for Wm Morrison Supermarkets (MRWSY) , which said Tuesday that group sales rose 2.9% from the same period last year and lifted its full-year earnings guidance.

In the first holiday season trading report for one of the U.K.'s "Big Four" supermarkets, Morrisons said the nine-week period that ended on Jan. 1 rose 5.2% on a like-for-like basis. It now expects its full-year underlying profit before tax to be ahead of the market's consensus and in the range of between £330 million ($400 million) and £340 million ($413 million).

Morrisons shares, which hit a two-year high, Tuesday, added a further 1.4% in early London trading to change hands at 249.50 pence each.

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