Wade-Gery has been widely tipped to fill chief executive Marc Bolland's shoes when he eventually departs the retailer, though her star waned somewhat last year when M&S's new online platform got off to a shaky start.
Shares in M&S have fallen 12% over the last month on Christmas trading concerns.
A second poor Christmas in a row is expected to put Bolland's position into question after five years in the job.
The firm is due to publish a third-quarter trading update on January 7.