The supermarket posted like-for-like sales growth of 2.3 per cent across the third quarter and 1.9 per cent in the six-week period to 6 January at its United Kingdom stores.
"I would describe the consumer as quite fragile and quite volatile and if there's a reason not to spend they take it", M&S Chief Executive Steve Rowe told reporters.
Marks & Spencer blamed a tough October for a 2.8 per cent fall in like-for-like clothing and home sales over the 13 weeks to December 30, while it said "ongoing under-performance" in its food arm saw sales fall 0.4 per cent.
This week's flurry of updates confirmed it was once again a highly-competitive Christmas for retailers, with online sales proving a key battleground and squeezed shoppers spending cautiously.
Ready to get started?
He said that but for October's unseasonable mild weather, M&S would have had a positive sales performance for clothing.
United Kingdom retailer Marks & Spencer has posted a 1.4% decline in like-for-like sales in its home market in its third quarter, with Food sales down 0.4% and Clothing & Home sales down 2.8%.
"We delivered an excellent operational performance across the group, with great availability, strong customer satisfaction scores and our lowest level of waste ever at Christmas", said Mike Coupe, CEO of Sainsbury's.
We've already had a first glimpse of that here on Monday where United Kingdom 2017 consumer spending fell for the first time in five years.
In November, M&S said it would speed up store closures, relocations and downsizings and re-position its food offer, including slowing down openings of "Simply Food" stores.
Clothing and homeware fell 2.8 percent, food also dropped by 0.4 percent despite being seen as the most successful sector.
Online sales at M&S.com lifted 3%, while its ongoing move to pull out of worldwide markets saw overseas sales slump 9.8%.
But Sir Charlie Mayfield, chairman of the partnership which owns the department store chain as well as supermarket Waitrose, admitted that pressure on profit margins had intensified amid rising costs thanks to the pound's Brexit-related weakness, and warned that trading would remain "volatile" for the year ahead.
That compared with analysts' average forecast of a 3.4 per cent decline and a second-quarter fall of 0.1 per cent.