A French court has sentenced a 28-year-old Damien Tarel to four months in prison for slapping France’s President, Emmanuel Macron, in the face.

The assailant was quickly arrested after the swipe that caught Macron's left cheek with an audible thwack on Tuesday, as the French leader was greeting a crowd.

The court in the south-east city of Valence convicted Tarel on Thursday on a charge of violence against a person invested with public authority. He was given additional 14-month suspended sentence, and was banned from ever holding public office and from owning weapons for five years.

Tarel described himself as a right-wing or extreme-right “patriot” and member of the gilets Jaunes economic protest movement. He shouted a centuries-old royalist war cry as he hit the President.

After the incident, Tarel acknowledged hitting the President with a “rather violent” slap. “When I saw his friendly, lying look, I felt disgust, and I had a violent reaction,” he told the court. “It was an impulsive reaction … I was surprised myself by the violence.”

He said he and his friends had considered bringing an egg or a cream pie to throw at the President, but had dropped the idea – and insisted that the slap wasn’t premeditated.

“I think that Emmanuel Macron represents the decline of our country,” he said, without explaining what he meant.

Tarel told the court that he supported the yellow vests economic protest movement that shook Macron's presidency in 2019. He told investigators that he held right- or ultra-right political convictions without being a member of a party or group, according to the prosecutor’s office.

The charge of violence against a person invested with public authority is punishable by up to three years’ imprisonment and a fine of €45,000 ($54,000).

Macron wouldn’t comment on the trial on Thursday, but said: “Nothing justifies violence in a democratic society, never.”

“It’s not such a big deal to get a slap when you go toward a crowd to say hello to some people who were waiting for a long time,” he said in an interview with broadcaster BFM-TV. “We must not make that stupid and violent act more important than it is.”

At the same time, the President added, “we must not make it banal, because anyone with public authority is entitled to respect.”

Another man arrested in the ruckus that followed the slap, identified by the prosecutor as Arthur C, will be judged at a later date, in 2022, for illegal possession of weapons.

The prosecutor’s office said that as well as finding weapons, police who searched the home of Arthur C also found books on the art of war, a copy of Adolf Hitler’s manifesto Mein Kampf and two flags, one symbolising communists and another of the Russian Revolution.