French President Emmanuel Macron said Saturday the law had to change to better protect victims of child sexual abuse, after thousands shared their stories in response to a newly published book.

"Today shame is switching sides" from victims to perpetrators, Macron said in a video posted to Twitter, welcoming the fact that "people feel free to speak everywhere in France".

The flood of testimony under the social media hashtag #Metooinceste followed the early January publication of a book, "La familia grande", by Camille Kouchner.

In it she accused her step-father, prominent political commentator Olivier Duhamel, of having abused her twin brother.

Macron did not directly address that case.

But in a short video posted to Twitter, he promised those speaking out online: "We are here. We're listening to you. We believe you. And you will never be alone again."

And he added: "We have to adapt our laws to better protect child victims of incest and sexual violence."

Promising to "punish criminals for their acts in the past and prevent them ever reoffending", Macron said the law would be updated.

In 2018, France already pushed back the statute of limitations for sexual crimes against minors to 30 years.

But some people have argued such acts should never fall beyond the reach of the justice system.

"No-one can ignore these experiences any longer," Macron said. "We have to hear and gather victims' testimonies even years, decades afterwards."

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