About 200 people attended the rally before [Tuesday's] council meeting to show their support for Mayor Caroline St-Hilaire, who wants to ban English at council meetings.
Bloc Québécois candidate Denis Trudel, who was at the rally, said he agrees with the mayor's position.
"We have to send a clear message — whether it's signs, the language of work, or the language in public institutions — a clear message that here, things are in French," said Trudel.
The protest comes after Robert Myles, a councillor from the borough of Greenfield Park, was called out by St-Hilaire for making his remarks to council in both French and English.
St-Hilaire said on her Facebook page that speaking exclusively in French is a matter of respect and common sense, because 95 per cent of the population understands French.
The conflict quickly escalated, with St-Hilaire receiving death threats over her comments.
The pro-French groups Impératif Français and Mouvement Québécois Français, along with the Bloc Québécois, are among those who have have come out in support of St-Hilaire.
In a speech to city council on Tuesday, St-Hilaire said she's neither a "racist," nor an "anglophobe," but she believes Longueuil is a French-speaking city.
"I assure you that nothing, absolutely nothing, will shake my determination or that of the City of Longueuil, to respect the legal status of Longueuil as a French city," she said.
St-Hilaire said she wants to put an end to the debate. She said any dispute about whether French should be the only language at city council meetings should be at the provincial level, rather than focused solely on Longueuil.
For his part, Myles said he has no plans to stop addressing council in French and English.
"I have citizens that I need to respect as their elected official, and that's what I'm going to continue to do," he said.
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