President Emmanuel Macron has upbraided a French teenager after the boy addressed him informally as "Manu" and sang the socialist anthem in front of him.

Mr Macron was attending a ceremony in northern France to commemorate General Charles De Gaulle's call for popular resistance during World War II.

The young man, who looked to be in his mid-teens, was standing behind a barrier as Mr Macron passed along the crowd.

He was captured on LCI television singing the words of the international socialist anthem before asking the President:

"Ca va Manu?" — which translates as "How's it going, Manu?"

"No, no, you are here at an official ceremony," Mr Macron, 40, told him sharply.

"You can't just behave like that.

"You can act like a clown, but today it's the 'Marseillaise' and the 'Partisans Song' we're singing.

"You address me as Mr President of the Republic or sir, ok?"

The boy, shaggy hair falling in front of his eyes, apologised.

"Sorry, Mr President," the teenager said.

Mr Macron stopped for selfies with other children attending the ceremony. ( AP-Pool: Charles Platiau )

But Mr Macron, who is known for his quick tongue and often mixes elevated language with street slang, went on:

"You need to do things the right way. Even if you want to lead a revolution one day, you've first got to earn a diploma and learn how to put food on the table," he said.

It's not the first time Mr Macron has been captured on camera giving lessons to those who challenge or disrespect him.

During the presidential campaign last year, a striking worker accused him of being a man in a suit.

"The best way to pay for a suit is to get a job," Mr Macron snapped back.

Reuters