A war of words between French President Emmanuel Macron and Brazil's Jair Bolsonaro ratcheted up this weekend after the latter took a swipe at the French First Lady.

Bolsonaro was enraged last week by Macron's decision to make the devastating Amazon wildfires a key item on the agenda at the G7 in Biarritz.

On Monday, Macron described Bolsonaro's comments as "extraordinarily disrespectful", adding: "I hope that they (Brazilians) will very quickly get a president who is up to the job."

'Don't humiliate the man'

As the leaders of the world's most-industrialised nations — Britain, Canada, France, Germany, Italy, Japan and U.S. — were in Biarritz for their annual meeting, Bolsonaro liked a Facebook post unfavourably comparing Brigitte Macron, 66 to his third wife, 37.

"You understand now why Macron persecutes Bolsonaro," Facebook-user Rodrigo Andeaca wrote.

Bolsonaro liked the comment and wrote: "Don't humiliate the man — LOL."

His post drew the ire of some users and journalists online who denounced it as sexist.

Academic and columnist Debora Diniz said Bolsonaro's "traditional macho sarcasm" was unleashed because he "is frightened by the international outcry of the burning of the Amazon."

The Brazilian Youtuber Felipe Neto branded it "disgusting" and "pathetic".

"Can you understand the level? Imagine the president of any serious country doing something like this. Seriously, try to imagine," he wrote on Twitter.

Asked about the post, a spokesperson for the Brazilian president's office told AFP: "No Comment."

'An an opportunistic moron'

But the attacks continued with Brazil's Agriculture Minister Abraham Weintraub labelling the French leader a "moron" for opposing the Mercosur trade deal.

Macron said he was against the free trade agreement between Brussels and Brasilia as it is because of environmental concerns including the fires in the Amazonian rainforest.

"France is a country of extremes. It has produced men like Descartes or Pasteur, but also collaborators" during World War II," Weintraub wrote on Twitter.

"(Macron) is just an opportunistic moron seeking the support of the French agricultural lobby," he added.

Bolsonaro's son, Eduardo, an MP, also got in on the action, addressing a "message to Emmanuel Macron" on Friday in the form of a video entitled "France in crisis — Macron is an idiot."

On Sunday, he also wrote that Macron "is under pressure from (French) farmers" adding: "it is unfortunate that he has such low conduct. It shows desperation for popularity."

'It's sad'

The French leader replied on Monday during a joint press conference with Chilean President Sebastian Pinera on the situation in the Amazon, saying the comments were "extraordinarily disrespectful to my wife."

"It's sad. It's sad. But it is sad first of all for him and for Brazilians. And so, I think that the women of Brazil are probably ashamed to read that of their president, I think that the Brazilians, who are a great people, are a little ashamed to see this kind of behaviour.

"As I have a lot of friendship and respect for the Brazilian people, I hope very quickly that they will get a president who is up to the job," he added.

He also said that no French ministers would insult a foreign leader in such a manner.