Economist Thabi Leoka has resigned from the board of MTN SA amid questions over whether she has a PhD from the London School of Economics.
The mobile network operator made the announcement shortly after Anglo American Platinum declared that she had stepped down from its board.
Both companies used the same language to announce her resignation, saying that the 44-year-old had stepped down to "attend to her health and the questions she has been facing concerning her academic qualifications".