Andrew Harrison, the former marketing director of Nestle who took over the Muller managing director role last year, instigated the review following a pitch for the creative business.
Harrison instructed the media auditor Billetts to oversee the pitch, which involved three other agencies including ZenithOptimedia.
In October, TBWA\London was appointed to handle the Muller creative account following a pitch managed by The Haystack Group.
Harrison ordered TBWA to create the brand's first masterbrand-style advertising campaign and the agency's debut work broke earlier this month, featuring the tagline "Lead a Muller life" set to the Nina Simone track I Got Life.
TBWA won the Muller creative account from Publicis, which had held it since 1999. One of Publicis' final spots for Muller, "budgie", prompted 142 complaints to Ofcom that it condoned animal cruelty, but it was exonerated.
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