Relatives of a 73-year-old gilets jaunes (yellow vests) protester who was seriously injured when French riot police pushed back demonstrators in Nice on Saturday are to file an official complaint for “wilful violence”.

Geneviève Legay was taken to hospital with a fractured skull after she was knocked over in a charge by officers wielding shields and batons at an unauthorised rally in the centre of Nice. Her condition was described as serious but stable. The French authorities have launched an inquiry into the incident.

On Sunday, Arié Alimi, a lawyer representing the Legay family, told the French broadcaster LCI: “We will be filing an official complaint for wilful violence with weapons and in a group by persons in authority over vulnerable people. And against the [police] prefect for complicity.”

Legay is believed to have hit her head on a pavement after the CRS (riot police) charged at protesters in an effort to disperse them from Place Garibaldi in the city centre. The local police authority had already officially declared the area off-limits to protesters.

There were conflicting reports on whether Legay was caught up in the police charge or knocked over by the crowd moving away from advancing officers.

Friends said Legay, who was carrying a large rainbow flag, was a campaigner for several groups, including theCGT union, and feminist and anti-racist groups as well as Attac, the anti-globalisation movement that campaigns for fiscal, social and ecological justice.

“She is engaged, and especially pacifistic,” Alimi said. “The police charge was very violent. The CRS saw three older people who were not moving and began to charge them. They had orders. I have never seen such scenes in our country for a long time. It has to stop.”

“You think it’s justified for the forces of law and order to charge older people, even if something is banned,” he added, referring to the ban on protesting.

Alimi said Legay had suffered skull fractures and other serious injuries. The lawyer said he would be filing a complaint on Monday morning.

Philippe Carenzo of the local group of Attac said: “She [Legay] was there to protest against the ban on demonstrating.”

This weekend saw the 19th consecutive Saturday of demonstrations by gilets jaunes since last November. French police, who have been criticised for their crowd control tactics and use of rubber bullets, were under orders to prevent a repeat of scenes on the Champs-Elysées the previous weekend where protesters rioted, looting and setting alight luxury shops, news kiosks and the exclusive restaurant Le Fouquet’s.

On Saturday, the French government drafted in troops to protect public buildings and banned demonstrators from the Champs-Elysées and other city centres including Nice, where Emmanuel Macron is due to meet his Chinese counterpart, Xi Jinping.

Saturday’s protests across France were mostly peaceful, though there were minor skirmishes between demonstrators and police. The interior ministry said 40,500 gilets jaunes protesters had turned out, with 5,000 of those in Paris. Gilets jaunes organisers claimed there were more than 127,000 protesters nationwide.