Even a traditional sing-song with a group of young Parisians is fraught with risk for a president attempting to persuade France to accept an unpopular increase in the pension age.

Emmanuel Macron had given a TV address on Tuesday regretting "no consensus could be found" on the reform when he went for a walk with his wife Brigitte.

He joined some men singing a song he remembered from his grandmother.

But it was shared by a Facebook group reportedly set up by the far right.

The young singers were part of a Parisian choir singing traditional songs on a street in the sixth district in Paris,

One of them approached President Macron asking him to join in a rendition of an old song from the Pyrenees called "Le Refuge", which he sang on a trip to the French mountain range last year.

The men, who were part of the local Saint Longin choir, were apparently using a mobile phone app to read the words of the song created by the Canto project.

Last October, left-leaning newspaper Libération revealed that the project, set up to promote the memory of traditional songs, had been founded and run by far-right activists.

Songs included French classics and nursery rhymes, but also others with a more questionable past including songs linked to the Spanish fascist Falange of the 1930s and Nazi Germany.

President Macron and his team are keenly aware of how viral videos can distract from the business of the day, especially when it comes to pension reforms.

His entourage told France Inter radio that after his TV address he was having some time to himself with his wife when they were approached by the singers.

"He then joined them for a Pyrenean song that he knows and is fond of. He couldn't have known at that moment the background of each of the people he was talking to," an official from the Élysée Palace was quoted as saying.

Last month another viral video showed how his relatively expensive watch magically disappeared in the middle of a TV interview.

It was a non-story as there was no evidence to back up claims that he was embarrassed by its opulence. The more obvious explanation was that it was banging the table. No matter, it was the tale that counted.

Likewise with the choir of Saint Longin.

The "narrative" has set in that the president was caught lending moral support for the far right, or was out carousing when the country was in crisis over pensions.

But the only link with the far right is that the founder of the app he was reading from was close to the National Rally opposition party.

The app's aim is to encourage communal singing. As well as being part-funded by the culture ministry, it includes plenty of revolutionary songs dear to the far left on its site, like "Ah ça ira", which features the friendly line "Aristocrats to the gallows!".

The choir are evidently from the Catholic right, but one of the singers, Géraud, told public radio station France Inter that their only link to the Canto project was that it had a repertoire of music they were interested in.

And, as the Élysée said, the president can hardly control who he and Brigitte Macron bump into on their night wanderings.

The story has legs because there is a video attached, and because the president is not in good odour at the moment.

That only makes it worse as he starts the Sisyphean task of building back his reputation.

He has now signed into law deeply unpopular reforms that raise the pension age from 62 to 64 and given Prime Minister Élisabeth Borne the job of leading 100 days of action, with a roadmap of major projects "at the service of France".

His impromptu sing-song on the streets of Paris may have been his first appearance in public since the reforms were forced through. But his second, on Wednesday, was due to be in daylight in the Alsace town of Muttersholtz, where he planned to relaunch his second term in office.

Security was tight as union leaders were planning a raucous welcome for the president, with protesters continuing to challenge his pension reforms.