At least 150 models were forced to wait for three hours or more in a hot and airless staircase for the Balenciaga show casting on Sunday.
With fashion already under intense scrutiny over under-age and overly thin models, the case made headlines around the world after US casting director James Scully broke ranks to denounce two rivals who he claimed were "serial abusers".
The furore has also highlighted how vulnerable even relatively top level models can be at "cattle call" castings for the elite catwalk shows in Paris, New York and Milan.
At least 150 models were forced to wait for three hours or more in a hot and airless staircase for the Balenciaga show casting on Sunday, with the agents shutting the door and turning off the lights when they went off to eat.
The label, one of the most influential on the Paris catwalk, sacked the casting agency on Tuesday hours after Scully took to Instagram to protest about the "sadistic and cruel" treatment of the women.
Despite repeated attempts, AFP has been unable to contact the casting director, who is a major backstage figure on the Paris scene.
Two models who were left in the dark told AFP that up to 300 girls had been forced to wait in the stairway over the course of the day, with the only toilet locked.
"It was the worst ever casting I had," said former Gucci model Anna Vivchar, 19, who lost her place when she had to go to the toilet. "Everyone was nervous and hot.
"I am very grateful Balenciaga did what they did. They also apologised and sent us flowers."
Fellow Ukrainian Elizabeth Pentsarska, 17, who has walked for Chanel, said with models rushing between up to 13 castings a day "normally you wait only maybe half an hour".
In a world where a code of silence often rules, and where models can be too afraid of losing work to speak up, insiders say the swift sacking of such a high-profile figure has sent tremors through the industry.
Isabelle Saint-Felix of Synam, the French model agency union, said the dismissal was a deterrent to those who would "abuse their power" over models.
"It is a warning to others and it could be an opportunity to rectify the situation. We have been warning for four or five years about the deteriorating situation.
"Things have to change. Sometimes we let things go too far before we open our eyes to what is going on," she said.
Synam had warned the French Couture Federation for years about "models being disrespected, worsening conditions and more and more demands," she said.
"Models are very sweet adorable girls who have very short careers. They want to work and think that this is the price they have to pay. But we say that is a price they should not have to pay."
Sara Ziff, a former top model who heads the New York-based Model Alliance, said the problem runs deep.
"The industry is completely incapable of regulating itself. It is a little bit sad that we are reduced to naming and shaming. Really we should have some standards in our industry."
Scully, who raised the alarm over the Balenciaga casting, sits on the board of the Alliance, which campaigned for child labour laws to be applied to underage models in New York.
Ziff, who directed the acclaimed behind-the-scenes fashion documentary "Picture Me", said: "You have to ask where were these girls' agencies? Aren't they supposed to be looking out for their interests? I think that's the real story."
She said models' concerns were often "trivialised and dismissed".
"It can't be that bad, people think. It is often not seen as work but more a privilege, but when you see what goes on behind the scenes there is nothing glamorous about it.
"You are going between New York, London, Milan and Paris in the span of a month, working around the clock going to castings and fittings and often you don't know your schedule sometimes more than a couple of hours in advance."
Working conditions in France tend to be better than in the US, Ziff said.
"In Paris, at least models are considered employees of their agents and their clients. In the US, we have almost no labour protection."