The account is worth an estimated 拢6m and covers activities including direct mail and direct response television.
Diane Franklyn, head of Which? marketing, said: "We will be developing a raft of new and innovative initiatives to attract new audiences to Which? and build our subscriber base for the future."
Watson Phillips Norman managing partner John Watson said: "We will be looking at a wide range of media and promotional techniques in order to build the audience for Which? in a way that is consistent with one of the most powerful brands in the minds of the consumer. It's a huge opportunity and we greatly look forward to the challenge."
The agency was appointed following a four-way pitch.
The appointment follows a number of wins for WPN. Recently it was appointed by VNU to promote its consumer technology title Computeractive, and prior to that it won the DM account for children's charity NCH.
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