The celebrated cartoonist of France's Le Monde daily Plantu said Friday that he would soon leave the paper after half a century of work that has seen him mock the elite in his country and elsewhere with bitingly acerbic drawings.

The departure on March 31 of Plantu -- who has championed cartoons as a bastion of free expression -- comes as a freedom of speech debate is raging both at the venerable paper and in France.

But Plantu, whose real name is Jean Plantureux, said his departure was not linked to the move this week by fellow Le Monde cartoonist Xavier Gorce to sever ties with the paper in a censorship row.

Plantu told AFP he would be taking his retirement when he turns 70 in March and his exit had nothing to do with Gorce's departure.

He said his cartoons would be replaced by drawings by Cartooning for Peace, an organisation he founded with former UN secretary general Kofi Annan 15 years ago to promote cartoons from around the world.

Plantu has created some 14,000 cartoons in his career, mainly for Le Monde, and has already handed most of his collection to the National Library of France (BNF).

No French president over the last half century has been safe from the mordant wit of Plantu, who has campaigned for UN cultural agency UNESCO to recognise newspaper cartoons as a fundamental human right.

Gorce quit Le Monde this week after the paper apologised for a cartoon where he sought to tackle a sex-abuse scandal that has rocked the French elite, saying "freedom cannot be negotiated".

Plantu said he supported Gorce. "I love his style. Seriousness is invading us, it's the cholera of the imagination," he told AFP.

Freedom of speech and its limits have been burning issues since Islamist gunmen massacred staff at the Charlie Hebdo magazine in 2015 after it had published cartoons of the prophet Mohammed.

A spate of attacks carried out by radical Islamists last year prompted President Emmanuel Macron to vow that France would never renounce its right to caricature.