Former 21st Century Fox chief executive James Murdoch, son of media tycoon Rupert Murdoch, has resigned from News Corps board, according to a document released Friday by the US Securities and Exchange Commission (SEC). A letter sent by James Murdoch to the board said the decision was due to "disagreements over certain editorial content published by the companys news outlets and certain other strategic decisions." News Corp owns the Wall Street Journal, the New York Post, The Times and the Sun newspapers among others, but not Rupert Murdochs Fox News network. James Murdoch was once seen as his fathers successor, but Fridays move reinforces his disengagement from the family media empire, which grew from a newspaper group in Australia. Murdoch, Ruperts younger son, headed 21st Century Fox until last year when he left after Disney acquired most of the groups assets. James Murdoch, 47, has recently been critical of his fathers business and its media coverage. In January, he denounced the climate change skepticism of some Murdoch media, citing coverage of the fires which devastated large parts of Australia. He has launched his own private holding company called Lupa Systems, which among other things has taken a stake in Vice Media.