The trial against two women who made false claims that France's first lady Brigitte Macron was transgender, sparking conspiracy theories among the far-right, opened on Wednesday.

The wife of president Emmanuel Macron sued self-proclaimed spiritual medium Amandine Roy and conspiracy theorist Natacha Rey for posting a four-hour long video to YouTube claiming that she had once been a man named 'Jean-Michel', which went viral weeks before the 2022 presidential election.

The defamation case began as Macron and his Renaissance party scramble to prepare for the snap election that was called following a massive victory for the far-right during the European Parliament elections earlier this month.

amandine roy
Self-proclaimed spiritual medium Amandine Roy posted a four-hour video to YouTube allowing a conspiracy theorist to make the false claims
The medium, 49, interviewed Rey, who did not turn up to the trial's commencement citing an illness, for hours on her YouTube channel in which she ranted about the 'state lie' and 'scam' that she claimed to have uncovered.

Rey was 'desperate to share her work', said Roy, who had merely 'acquiesced to her request'.

Despite this claim of acquiescing to Rey, Roy said the conspiracist 'had spent three years researching, it's not like she pulled it out of her hat'.

'My regret is that this wasn't taken up and investigated by the mainstream media,' said Roy, who said she could not 'hide' such a 'serious' subject.

Neither the president, 46, nor the 71-year-old first lady were in court. She is demanding €10,000 in compensation for her and her brother Jean-Michel, who she says was caught up in the conspiracy.

Following the release of the video, online theorists accused the first lady, formerly Brigitte Trogneux, of never existing in the first place, claiming that her brother Jean-Michel had changed gender and assumed a new identity.

The false claim also led to more serious accusations of child abuse brought against France's first lady.

'The prejudice is massive, it exploded everywhere,' said Brigitte Macron's lawyer, Jean Ennochi.

The disinformation even spread to the United States where Brigitte Macron was attacked in a now deleted YouTube video ahead of the November elections.

Brigitte Macron is among a group of influential women - including former US first lady Michelle Obama and New Zealand ex-premier Jacinda Ardern - who have fallen victim to the growing trend of disinformation about their gender or sexuality to mock or humiliate them.

A decision on the case is due to be made on September 12.

In the meantime, the first lady's husband has to deal with a frantic election battle following his decision to call a snap election, which blindsided many.

The two-round election will take place on June 30 and July 7. Many are worried that the far-right in France will ascend to power, given their surprise victory at the European Parliament election earlier this month.