French prosecutors have dropped an investigation into incestuous sexual abuse of a 14-year-old by a prominent French political commentator, a case that unleashed an online movement against similar abuse.

The Paris prosecutor's office had been investigating political scientist and media commentator Olivier Duhamel on potential charges of raping his adolescent stepson in the 1980s, but said in a statement Monday that the alleged abuse took place too long ago to prosecute.

The prosecutor's office suggested that the accusations were substantial enough to justify judicial proceedings if there hadn't been a statute of limitations.

The accusations became public in January in a book by Duhamel's stepdaughter, Camille Kouchner, who described alleged abuse of her twin brother when they were 14. She wrote that they had spoken about it at the end of the 2000s with family members and friends, but no one sought to hold Duhamel accountable.

The book sparked an online #MeTooInceste movement in France that led to tens of thousands of similar testimonies.

Duhamel resigned from his role at the prestigious Sciences Po university and his media engagements after the accusations emerged. French media reports have said that Duhamel acknowledged the sexual abuse to investigators.

It was among several high-profile cases of alleged sexual abuse of minors in France that prompted new efforts by the government this year to set an age of consent and make it easier to prosecute historic crimes by extending statutes of limitations.