The move is the latest blow to embattled Andersen, which continues to lose clients in the wake of the Enron Corp. meltdown.
A WPP spokesman said the decision involved a review but was heavily influenced by the hiring by Deloitte of a significant number of Andersen's staff. Deloitte has acquired part of Andersen's London practice.
Shareholders will be asked to vote on the selection of Deloitte at WPP's annual general meeting June 24.
Andersen currently handles auditing for Omnicom Group, Havas Advertising and Bcom3 Group as well. Both Havas' and Omnicom's management have said they are watching the situation, while Bcom3's appointment should become academic in September, when its acquisition by Publicis Groupe is completed.