The business has been held by Walker Media, which is majority-owned by Publicis Groupe, since 2000. The agency is involved in the current pitch process.
A spokeswoman for M&S said: "We regularly review our agencies to ensure that we are getting the best possible service."
Steven Sharp, M&S’s long-serving marketing chief, stepped down in February. He was replaced by Patrick Bousquet-Chavanne, the former Estée Lauder group president.
The latest iteration of M&S’s "leading ladies" campaign celebrating influential British women will launch on Monday.
The activity, including print executions shot by the renowned US photographer Annie Leibovitz, was created by M&S’s long-standing ad agency Rainey Kelly Campbell Roalfe/Y&R and features Emma Thompson and Annie Lennox.
M&S also used well-known figures in its fairytale-inspired Christmas campaign, starring the brand ambassadors Rosie Huntington-Whiteley and David Gandy alongside the actress Helena Bonham Carter.
The retailer has experienced falling clothing sales for ten consecutive quarters. General merchandise sales, which are primarily clothing, declined by 2.1 per cent in the three months to the end of December 2013.
However, food sales have performed better and were up 1.6 per cent across the same period.
M&S gained significant loyalty online during the duration of the Christmas campaign, attracting almost 265,000 new Facebook fans, according to We Are Social.
Publicis Groupe bought a 75.1 per cent stake in Walker Media from its parent, M&C Saatchi, in November last year. The agency will form the "cornerstone" of a new global media network.