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.

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, Britain's second-largest grocer, was the only member of the so-called "Big Four" to increase its market share, the researcher said.

"The polarisation of the market is highlighted by consumer spend levels which were widely anticipated to drop this year," said Kantar director Edward Garner. "While 47% of shoppers did reduce their spend in the lead up to Christmas, 48% of shoppers increased their spend by 4.5% (the rate of inflation) showing that 'two nations' continues to be a key feature of the grocery market."

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.

Grocery market inflation, Kantar reported, surged a full one percent - to 4.5 percent for the 12 week period from its previous reading (the 12 weeks ending on 25 November). Kantar measures the price rises based on a weighted average of 75,000 products marked over a year-on-year basis.

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.

The accountancy and consulting group BDP LLP said Monday that like-for-like sales increased by 1.9 percent for Britain's larger retailers in the five weeks that ended on 29 December, thanks to a wave of online shopping and bargain hunting.

The group's annual High Street Sales Tracker said online sales surged 30.9 percent from the same period last year, while footfall on the weekend before Christmas was up 22 percent.

William Morrison Supermarkets, Britain's fourth-largest grocery store chain, reported disappointing Christmas sales figures Monday as investors prepare for a critical week of updates from major food retailers.

The Bradford, England-based group said overall like-for-like sales for the 6 weeks ending on 30 December declined by 2.5 percent. Sales not including fuel fell by 0.9 percent from the same period last year, the company said in a trading update.

"The well-publicised under-performance of Morrison's continues and it is the only big four supermarket to lose sales compared with last year," said Kantar's Garner. "This highlights its need to address the lack of convenience outlets and an online offering in 2013, as already clearly identified by the retailer."

Sainsbury's will publish its December sales update Wednesday, followed by Tesco figures on 10 January.