This week, Danone said Faber - who until now has combined the CEO and chairman roles - would stay on as chairman and oversee the search for a new chief executive.
"With Mr. Faber as chairman, the incoming CEO will not have the appropriate latitude to set a new direction," wrote Artisan, which has a stake of around 3% in Danone.
Artisan Partners' letter to Danone's board of management echoed a similar position from investment company Bluebell, which also said Danone should appoint another independent chairman instead of Faber.
Activist investors say Danone - whose brands include Evian and Actimel - needs a management revamp as they believe that under Faber's tenure, Danone's sales growth, margins and share price have lagged rivals, including Perrier-owner Nestle and Unilever, the maker of Cornetto ice cream and Lipton tea.
(Reporting by Gwenaelle Barzic, Benoit Van Overstraeten, Sudip Kar-Gupta; editing by Jason Neely and Louise Heavens)