J Sainsbury plc said it had record sales over the key Christmas period but warned of a challenging market for British retailers in the months to come.

The UK's second-largest grocery store chain said like-for-like sales grew by 1.5 percent in the 14 weeks ending on 5 January, the company said in a trading update published on its website. Excluding fuel, the sales advanced 0.9 percent. Total sales for its fiscal third quarter rose 3.9 percent, the company said, maintaining a pace of 32 consecutive quarters in which the company has grown its top line.

"This Christmas we have helped more customers than ever to Live Well for Less, delivering another quarter of good sales in a challenging retail environment, increasing market share," said CEO Justin King. "We saw a record breaking £16m of sales in one hour between 12pm and 1pm on Sunday 23 December and experienced our best ever Christmas Eve, at both our supermarket and convenience stores, with over £100m of sales."

The group's online sales advanced more than 15 percent, the company said, while its Convenience division saw an expansion of 15 percent. The group said it was "well positioned" heading into its fiscal fourth quarter and would update the market on trading for that three month period on 19 March.

Britain's biggest grocery stores fought through a competitive holiday trading season with little market share gains from last year, the research group Kantar Worldpanel reported ahead of key Christmas updates from the three biggest chains.

King told investors on a conference call following the update that his is confident that Sainsbury's would emerge as the clear 'Christmas winner' of the so-called "Big Four" UK supermarkets once all the companies have published thier updates. Tesco will report its Christmas trading update on 10 January and some analysts suggest Britain's top retailer will post sales figures than Sainsbury's for the first time since 2010 a £1bn revamp of its key UK market earlier this year.

Overall grocery store sales grew 3.2 percent in the 12 weeks ending 23 December, Kantar said in a report published on its website Tuesday, with the strongest growth coming from the discount and premium ends of companies product ranges. J Sainsbury was the only member of the Big Four to increase its market share, the researcher said.

Tesco, Britain's biggest retailer, saw its market share dip to 30.5 percent from 30.6 percent during the period, Kantar said, arresting the average 0.4 percent decline the group had been experiencing for most of the year. Discount retailer Aldi, on the other hand, recorded an all-time hig 3.2 percent market share gain following sales growth of 30.1 percent for the period. Rival discounters Lidl (10.8 percent) and Iceland (2.2 percent) also showed improvements.

High end grocery store chain Waitrose saw 5.4 percent sales growth, Kantar said.

The British Retail Consortium said Tuesday that like-for-like sales across the country in December rose a modest 0.3 percent last month, with the lobby group describing the Christmas sales season as "underwhelming" owing to muted consumer confidence and an overall lack of optimism from British shoppers.

Online sales, however, remained the bright spot for UK retailers, rising 20 percent last month, the BRC said, from an annual monthly average of around 12 percent.

Sainsbury's shares rose 0.18 percent in early London trading to change hands at 339.6 pence each. The shares have advanced more than 12.4 percent over the past year.