National Amusements third-gen Shari Redstone was the only vote from the board of directors at Viacom, her family's media empire, opposing the appointment of Philippe Dauman as chairman on Thursday.
Her father, Sumner Redstone, 92, announced his retirement on Thursday. He had announced his retirement as chairman of the family's other media empire CBS on Wednesday, where he will be replaced by its existing CEO and president Leslie Moonves.
Sumner Redstone's father founded theatre company National Amusements, which controls CBS and Viacom, in 1936. Today it operates more than 1,500 movie screens across the globe.
Shari is president of National Amusements, and also runs Advancit Capital, which invests in new media.
She had made it clear she would not like Philippe Dauman, its existing CEO, to succeed her father.
"It is my firm belief that whoever may succeed my father as chair at each company should be someone who is not a trustee of my father's trust or otherwise intertwined in Redstone family matters, but rather a leader with an independent voice," Shari said in a statement. "I was honored to nominate Les as the CBS chair and am delighted to congratulate him on his new position." Dauman is a trustee of her father's trust.
Over the last year, Redstone has been forced to defend his role at the helm of both family empires, with investors and media speculating about his ailing health.
In a statement released in May, Redstone said that any decision on succession would be made by the boards of CBS and Viacom, rather than an individual, adding that he cared strongly about professional management and good corporate governance.
"After my death, my ownership interest in the companies will be overseen by a group of seven trustees who will make fiduciary decisions based solely on the best interests of the beneficiaries of the trust.”
Redstone's son, Brent Redstone, sued the family in 2006 over the running of its business interests, arguing that his sister was favoured over him and that he had been shut out of the company affairs. It was settled out of court the following year.
Redstone has been married twice, with both ending in divorce. Last September, he separated from his 44-year-old girlfriend Sydney Holland.