The Broadway League, the trade association of Broadway producers, have brought a legal complaint against the New York theater industry’s biggest casting directors, branding the casting companies as a “cartel” that is violating antitrust laws in its current efforts to unionize.

The League filed the complaint early Tuesday morning against companies including Telsey & Co. and Tara Rubin Casting, as well as the Casting Society of America and the Teamsters Local 817, the labor union that has joined the casting directors in the push to unionize. The two sides have been deadlocked in a contentious battle over the issue for months; the League’s filing alleges that the casting directors’ actions amount to a “conspiracy [that] threatens to irreparably destroy competition for decades to come.”

“The defendants continuing illegal and anticompetitive cartel behavior is jeopardizing the survival of Broadway shows, and bringing real harm to the actors, stagehands, musicians, and others who depend on the theater for their very livelihood,” said Charlotte St. Martin, the Broadway League president, in a statement. “We have no choice but to seek a legal remedy to the cartel’s illegal behavior.”

Teamsters 817 president Tom O’Donnell said, “The casting directors are not attempting to ‘fix prices’, neither in wages nor benefit contributions. They simply want the same workplace fairness and healthcare afforded to everyone else who works on Broadway.” He added, “Rather than engage in a dialogue with forty working men and women who have been instrumental to their success, the League spouts fake facts, bullies, and files lawsuits.”

The League’s action comes after casting directors began to get serious about their demands last month, collectively refusing new work unless producers agreed to increased fees for what casting directors labeled as “pension and welfare benefits” but the League’s complaint calls “a 29% surcharge.” In its suit, the League calls the standoff a “boycott” that aims to jack up prices and eliminate competition unfairly.

At the heart of the issue is whether casting companies can be deemed employees or independent companies. In their attempts to unionize, the casting directors have positioned themselves as employees hired by producers for individual productions; the League’s pushback labels them independent companies, each of which funds and develops a proprietary database of performers used to cast actors across  shows for multiple independent producers.

The League filed the complaint in the United States District Court for the Southern District of New York.