Supermarket Sainsbury's has emerged as the sector's winner so far in the run-up to Christmas as it became the only one of the major players to notch up a rise in sales.
The chain, whose Christmas advertising campaign features popular children's book character Mog the Cat, saw sales rise 1.2% in the 12 weeks to December 6 and grew its market share to 16.7% from 16.5% a year earlier, according to Kantar Worldpanel.
But Tesco suffered further trading woes as its sales dropped 3.4% in the quarter, while its market share fell to 28% from 29.1% a year earlier.
Embattled Asda and Morrisons were also hit by falling sales - down 3.4% and 2% respectively.
Walmart-owned Asda has lost its position as the UK's second biggest supermarket in recent months, having been overtaken by a resurgent Sainsbury's.
Asda's market share stood at 16.2% in the 12-week period, down from 16.7% a year ago, while Morrisons also saw its share dip to 11% from 11.2%.
Figures also out for the same period from supermarket analysts Nielsen confirm a similar picture, with sales down 3.1% at Tesco, 4.3% at Asda and 2.1% at Morrisons, while Sainsbury's enjoyed a 0.5% increase.
Both Kantar and Nielsen said there was little benefit from Black Friday, with the supermarket sector being hit by falling food and drink prices as a price war continues to rage on.
Kantar said the one-day sales bonanza boosted sales on the Friday by 4% against the previous Friday, but added it had "done little to buoy the market overall".
Its data showed the sector as a whole saw sales rise by 0.1% in the 12 weeks - the lowest growth since June and the ninth consecutive month where sales have increased by less than 1%.
Fraser McKevitt, head of retail and consumer insight at Kantar, said Sainsbury's was benefiting from strong shopper demand for its Taste the Difference range, with sales of champagne and sparkling wine up by a quarter.
It has also been boosted by its well-received "Mog's Christmas Calamity" advert, starring the character from Judith Kerr's book.
But Mr McKevitt said: "Sainsbury's recent run of success predates its popular 'Mog's Christmas Calamity' advert, with the retailer now having grown ahead of the market for three months in a row."
Discounters Aldi and Lidl once again saw double-digit sales growth, up 15.4% and 17.9%, according to Kantar.
They now hold a 10% share of the market between them, with their growing popularity driving prices down across the sector as the Big Four try to keep pace.
Mr McKevitt added shoppers would benefit from food price deflation, as Kantar's research showed grocery prices fell by 1.9% in the 12-week period.
He said: "Although slow growth means a distinct lack of seasonal cheer for the market, the news is more positive for consumers looking to save this Christmas.
"Last year customers spent an average of £71.33 on their big Christmas shop but with falling prices set to continue, shoppers are likely to enjoy a cheaper Christmas this year."