A well-known French urologist, named as a member of a new commission to investigate online conspiracy theories and hate speech, resigned on Thursday, citing a "smear campaign" against him.

Professor Guy Vallancien, a urologist with celebrity clients, said he was resigning from the commission after a "shameful, appalling and untruthful smear campaign".

"I decided to leave and I told the president's office. I could have stayed but it would have created tensions within the commission and there's no point. There were no good solutions," he explained.

The commission on conspiracy is being chaired by sociologist Gerald Bronner. The panel, announced by President Emmanuel Macron in late September, includes 15 experts from various fields who were asked to produce a report by the end of the year on how to combat conspiracy theories, disinformation and online hate speech.

Vallancien's nomination had been publicly criticised by famed French whistleblower Irène Frachon who helped to reveal deaths linked to a popular weight-loss and diabetes pill called Mediator which was sold for decades in France.

Frachon accused Vallancien of being one of a number of high-profile doctors who had "over many years tried to discredit, play down or even deny the seriousness of the human costs of Mediator".

Marianne magazine also revealed how he was recently sanctioned for issuing a false medical certificate, while L'Express magazine reported how he was director of a medical school embroiled in a scandal over the neglect of human bodies donated for research.

Vallancien denied any responsibility for the scandal at the Universite Paris-Descartes, which emerged in 2019.