M&S sales up 9.4% y/y in 12 weeks to Jan. 1 - NielsenIQ M&S will publish its own trading statement on Thursday M&S shares up 1.6%, up 92% over last year LONDON, Jan 11 (Reuters) - Marks & Spencer (MKS.L) was Britain"s fastest growing food retailer in the key Christmas quarter, market researcher NielsenIQ said on Tuesday, providing further evidence that the company"s latest turnaround programme is gaining traction. NielsenIQ said M&S"s grocery sales soared 9.4% in the 12 weeks to Jan. 1 from the same period a year earlier, with growth accelerating from its previous report. read more In November, M&S said it had beaten forecasts for first-half profit and upgraded its earnings outlook for the second time in three months, sending its stock soaring on bets that one of Britain"s most elusive turnarounds could finally materialise. read more M&S shares were up 1.6% at 0915 GMT, extending gains over the last year to 92%. Some analysts believe M&S, which also sells clothing and homeware, could upgrade its 2021-22 profit outlook again on Thursday when it publishes its own third-quarter trading update. read more NielsenIQ"s data showed market leader Tesco (TSCO.L) was the best performer of Britain"s so-called Big Four grocers. Its 0.1% sales decline significantly outperformed Sainsbury"s (SBRY.L), Asda and Morrisons which had falls of 4.2%, 3.1% and 5.6% respectively. That data echoed data from rival market researcher Kantar published last week. However, Kantar does not include M&S in its monthly reports. read more NielsenIQ noted, however, that M&S had weaker comparative sales numbers than the Big Four in 2020. The researcher said UK shoppers spent a total of 7.1 billion pounds ($9.6 billion) at supermarkets in the two weeks to Dec. 25, up from 6.7 billion pounds in 2020. Sainsbury"s will give an update on its Christmas trading on Wednesday, while Tesco will provide an update on Thursday. The British arm of German discount supermarket group Aldi said on Monday its sales in December rose 0.4% compared with the previous year, while rival Lidl GB said on Tuesday its December sales rose 2.6%. read more ($1 = 0.7374 pounds)