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, said Scully, who claimed the agents shut the door and turned off the lights when they went 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.
But Maida Gregori Boina, the casting director involved -- a major backstage figure on the Paris scene -- hit back Friday, blaming Balenciaga and denying the allegations as "inaccurate and libellous".
"We provided the most comfortable accommodations allowable based on the facilities provided," she said in a statement.
Boina denied that she had turned off the lights or locked the door on the waiting models, blaming an electricity cut late on Sunday at Balenciaga's Paris headquarters.
Models who were left in the dark told AFP that girls had been forced to wait in the stairway over the course of the casting, with the only toilet locked.
