Supermarket giants Sainsbury‘s and Tesco have both seen sales grow 3.9 per cent over the Christmas period while their market share remains unchanged from the same period last year, according to new data released today.

Consumer insights firm Kantar Worldpanel has revealed that the pair posted identical growth rates for the six weeks ending January 6th 2013, just days after the grocers butted heads over their respective festive sales figures.

Last week, a senior member of Sainsbury‘s investment relations team alleged that Tesco‘s headline sales number in its Christmas trading results was misleading, calling the figure “a bit disingenuous” in an email to Sky News.

While Tesco chief Philip Clarke made no comment on the accusation, Edward Garner, Director at Kantar, noted that today‘s data highlights an undoubted turnaround in the supermarket‘s fortunes.

“These festive trading figures show a dead heat between Tesco and Sainsbury‘s in the battle for Christmas,” Garner explained.

“Both posted identical growth rates of 3.9 per cent – just ahead of the total market – and market shares unchanged from a year ago.

“This represents a clear improvement in Tesco‘s fortunes following a series of share dips in 2012 but it is also a strong performance from Sainsbury‘s which had been predicted to suffer disproportionately from the Tesco fight-back by some commentators.”

Recording a market share of 30 per cent over the period, Tesco‘s has maintained it‘s lion‘s share of the hugely competitive grocery market while Sainsbury‘s share currently sits at 17.1 per cent.

Meanwhile, competitor Asda saw sales growth of 2.1 per cent during the festive season while market share decreased 0.2 per cent on the same period last year to 17.7 per cent, though Garner pointed out that this figure has been affected by its acquisition of Netto stores and is “strong by historical standards for this period.”

Last week, Morrisons reported a like-for-like sales drop of 2.5 per cent for the six weeks ended December 30th 2012 following a “challenging” Christmas, and as such its sales growth has fallen one per cent, according to Kantar while its market share has fallen from 12.5 per cent last year to 11.9 per cent, emphasising the ongoing struggles for the company as it builds its multichannel operations.

Upmarket grocer Waitrose, which has long had an online presence and has a strong click & collect offer across its stores, saw its market share rise 0.3 per cent to 4.9 per cent as sales growth reached 8.6 per cent over Christmas.

Applauding its performance, Garner said: “Waitrose‘s strong performance over the seasonal period is reflected in its 8.6 per cent growth rate, which is over twice the market average.

“Although this six week report is, strictly speaking, not comparable with our usual 12-week series it is worth noting that the Waitrose share is higher than any previous share we have reported for the retailer.

“Elsewhere, shoppers continued to seek value for money with ongoing positive performances for Aldi, Lidl and Iceland.”