Mion first expressed surprise at the incest allegations against Duhamel, which came to light after the publication of a book by the alleged victim's twin sister, Camille Kouchner, but he later admitted he had been told of the accusations in 2018.
In mid-January the higher education minister launched an investigation into how the school handled the affair. In a letter to students and staff on Tuesday, Mion said he had decided to resign after the preliminary report called into question how he handled the situation.
"The report...points to errors in judgement in my handling of the allegations which were communicated to me in 2018, and inconsistencies in the way I communicated about this case after it arose,” he wrote, pointing out that the report also found no systemic cover-up by the university. “I understand the resulting turmoil and take full responsibility for it."
Duhamel resigned last month from his post overseeing the university.
There are many questions in France about who knew what and when, and the publication of the book helped bring the previously taboo subject into a national spotlight.
It prompted hundreds of people to come forward on social media with their own stories of incest, including Sciences Po students. It has also pushed President Emmanuel Macron to call for legislation on incest to better protect children.
(with wires)
