It is unclear how much business Bright has secured and what it means for Which?'s relationship with Rapier.
Rapier has held the £14m Which? marketing account since December 2003.
Rapier helped last year in the rebranding of the Consumers Association' to Which?, named after its well-known magazine, and produced direct marketing aimed at young families and homeowners.
It was appointed by marketing director Geoff Hurst, who left last year and was replaced by Chris Gardner.
Rapier is not believed to have produced work for Which? this year.
Neither the client nor Rapier could be reached for comment at the time of writing.
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