According to reports, the retailer withdrew its ads in January, following a complaint it made about a story in the Mail on Sunday.
The report, published last winter, claimed that the retailer "had secretly made moves to sell up to half of its poorly performing Simply Food convenience stores". It was corrected after the complaint, but M&S management remained unhappy about the newspapers' stance.
The retailer's declared aim of winning its traditional customer base back could be harmed by lack of access to Mail and Mail on Sunday's readership. Both sell more than 2.4m copies.
Neither M&S nor Associated were willing to comment. M&S's media agency, Walker Media, also refused to comment.
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