Marks and Spencer saw sales fall over the key Christmas period, while Tesco reported record festive trade.
M&S said its like-for-like revenues fell 1.4% in the 13 weeks to 30 December. Clothing and homeware fell 2.8%, while food, seen as its most successful sector, was down 0.4%.
By contrast, Tesco’s UK sales rose 2.3% in the 19 weeks to 6 January.
The supermarket said it saw “record sales and volumes” in the four weeks leading up to Christmas Day.
The two retailers’ trading updates came on a day of big news for the UK’s High Street giants that also saw John Lewis release figures for the Christmas period.
John Lewis said its gross sales for the six weeks to 30 December were up 2.5% on the same period in 2016.
Waitrose supermarket, which it also owns, reported a 1.4% increase in sales.
All three major retailers alluded to difficulties in the market and tough trading conditions, with Tesco speaking of “inflationary pressures” and M&S referring to “ongoing trading pressures”.
M&S chief executive Steve Rowe said it had been a “mixed quarter”, with “a weak clothing market in October and ongoing underperformance in our food like-for-like sales”.
He added: “Our revenue grew both in-store and online over the weeks leading up to Christmas, and we held our full-price stance in a very promotional market and did not participate in Black Friday.
“However, the impact of an unseasonal October resulted in an overall revenue decline.”
Bryan Roberts, global insight director at marketing firm TCC Global, said: “While we expect 2018 to finally see some genuine signs of a turnaround in M&S’s womenswear business, the trading over Christmas was disappointing.
“A last-minute rush proved too little, too late to rescue the overall period.
“It is within food that many rivals have closed the gap on M&S in terms of innovation and premium ranges, while also putting M&S’s prices in sharp relief. We would like to see a simpler pricing architecture with less reliance on multi-buys.”
Meanwhile, Tesco said it was “confident” in its full-year outlook following its performance over Christmas.
Chief executive Dave Lewis said: “We have continued to outperform the market throughout this period, particularly in fresh food, thanks to our most competitive offer for many years.”
Natalie Berg, global research director of Planet Retail, told BBC Breakfast that Tesco would never return to its former glory, but had responded well to its difficulties.
She added: “The ship has been steadied and they’re doing all the right things.”