LONDON (Reuters Breakingviews) - Investors have soured on yoghurt maker Danone. Activist Bluebell Partners wants the 38 billion euro company to split the role of chairman and chief executive and for boss Emmanuel Faber to step down. Underperformance during his tenure makes a convincing case for at least doing the former. Since October 2014 when Faber became chief executive, the Activia maker returned 24% to shareholders, compared to 109% at Unilever and 73% at Nestlé, according to Refinitiv data. He has also presided over a series of earnings misses and sluggish top-line growth, and a 10% post-tax return on invested capital lags the high-teens levels boasted by Nestlé and Unilever. Danone’s specialised nutrition business, which includes food for infants and hospital patients, has struggled. Despite jumping onto the plant-based trend early, with its pricey acquisition of Alpro maker WhiteWave Foods in 2017, Danone has faced challenges from faster growing upstarts like Oatly. French protectionism normally makes life difficult for activists, but Bluebell’s views should gain support. Combining the roles of chairman and chief executive may be palatable at outperforming groups like L’Oréal, but not when you are adrift of peers. While Danone recently chose a new independent board member and announced plans for two others in December, its mostly French directors would benefit from more external consumer goods experience. The recent appointment of former Chief Financial Officer Cecile Cabanis to the board, almost immediately after her resignation, sent the wrong message. The bigger problem for Faber is the complexity of the problem he must fix. He has started by reorganising the company by geographies and considering some minor divestments, though not anything radical like selling water. After years of poor excuses, Danone also needs to be more transparent by reporting on both geographies and product lines, like Swiss rival Nestlé. Conventional corporate governance wisdom has it that chief executives and chairman shouldn’t be replaced at the same time. As such, the priority should be a tough chair that can push Faber to ensure Danone returns to profitable growth by the second half of this year, as he has promised. He or she could use the intervening time to locate a new chief executive should the chief executive again fail to deliver.