Next has said it expects like-for-like retail sales to fall between 3.5 percent and 6 percent in its second half.
Analysts see a better performance at its Directory home shopping business, with forecasts ranging from a small fall to a small rise.
Associated British Foods said in September it expected "some progress" in adjusted earnings for the year ended September 12, up from its previous forecast of a flat result. That was thanks largely to a 7 percent rise in underlying sales at Primark over the year.
Next shares have matched the UK non-food retail index this year, while M&S has underperformed by 4 percent.
(Editing by Jon Loades-Carter)