Sciences Po’s director has resigned over his handling of an incest scandal involving professor and political commentator Olivier Duhamel that has shaken French academia and triggered other public accusations against prominent intellectuals.

In an open letter to the teachers and students of France’s most renowned political sciences university, Frédéric Mion said a preliminary report by education inspectors cited “errors of judgment” on his part in the way he dealt with allegations brought to his attention in 2018 and “inconsistencies” in his public statements of recent weeks. The report has exonerated Sciences Po of any complicity.

“I have decided to present my resignation to the members of our boards and the minister of higher education,” he wrote. “I hope that this will allow the return of the calm so necessary for everyone’s work.”

The resignation comes as students of other political sciences schools that are part of the Sciences Po network across France have alleged they have been victims of sexual assaults, and that staff did little to address their complaints. Sciences Po said on Twitter it “fully supports victims of sexist and sexual violence”.

In his letter, Mion said the preliminary inquiry had found that “Sciences Po, under my direction, has resolutely engaged in the struggle against all forms of sexist or sexual violence”.

Duhamel, a prominent constitutional law professor, is being investigated by the state prosecutor although his alleged crimes in the 1980s appear to fall under the statute of limitations in force at the time. He has been accused by his stepdaughter Camille Kouchner of sexually abusing her twin brother when he was 13 or 14.

When Kouchner’s book detailing the allegations was published at the start of the year, Duhamel resigned as president of the National Foundation of Political Science, which oversees the running of Sciences Po, and from other positions including his presidency of the elite dining club Le Siècle. He did not comment further than citing the fact that he was the target of “personal attacks.”

Mion said then he was “stunned” by the allegations, acknowledging he should have taken what he took to be “a rumour circulating about Olivier Duhamel” more seriously. “I let myself be fooled,” he told Le Monde.

Kouchner’s book, and the various allegations aired since by other victims of incest and sexual abuse, are the latest sign of a shift in French opinion away from what is now viewed as excessive permissiveness in the decades following the 1968 uprising.

In recent weeks, thousands of people have taken to social media, using the hashtag #metooinceste on Twitter, to denounce alleged abusers. The attention paid to incest since Kouchner went public follows similar campaigns against figures from the world of the arts and sports for alleged sexual abuse of teenage girls.

Among those targeted are Jean-Luc Brunel, a former French model agency boss and associate of the late sex offender and financier Jeffrey Epstein, who is being investigated for “rape of a minor over 15 and sexual harassment”, and Gabriel Matzneff, now 84, the French author who wrote books about his sexual relations with adolescents and children.

Additional reporting by Alice Kantor in Paris