This month, claims spread across the social media platform that the first lady of France was born as a man named Jean-Michel Trogneux.

The 63-year-old wife of French president Emmanuel Macron will now sue the instigators of the conspiracy theory, Paris-based newspaper Le Figaro reported.

For several days in mid-December, the hashtag #JeanMichelTrogneux was trending in France on Twitter, according to the newspaper.

The rumour started when right-wing journal Faits et Documents published an article in September claiming it had conducted a three-year investigation into Ms Macron and that its theory was supported by many experts, French outlet CNews reported.

It is not the first time high-profile political women have been dogged by false rumours surrounding their sex.

Unsubstantiated claims have circulated online that former US First Lady Michelle Obama was born a man, with the name Michael Lavaughn Robinson.

New Zealand prime minister Jacinda Ardern has also reportedly been a victim of conspiracy theories about her sex.