A tennis union co-founded by Novak Djokovic on Tuesday announced a series of legal actions aimed at the sport's governing bodies, alleging "anti-competitive restraints and abusive practices".
The Professional Tennis Players' Association (PTPA) said it was suing both tour organisers, the Association of Tennis Professionals (ATP) and the Women's Tennis Association (WTA).
The International Tennis Federation (ITF), and International Tennis Integrity Agency (ITIA) were also named as defendants in a series of actions in the United States, United Kingdom and the European Union.
Both the ATP and WTA responded by vowing to defend themselves against the claims with the men's tour saying the PTPA has "consistently chosen division and distraction through misinformation over progress".
The PTPA was set up by Djokovic and Canadian Vasek Pospisil in 2020.
Some 20 players were named as part of at least one of the actions.
"The lawsuits expose systemic abuse, anti-competitive practices, and a blatant disregard for player welfare that have persisted for decades," said the PTPA statement.
"The ATP, WTA, ITF, and ITIA operate as a cartel by implementing a number of draconian, interlocking anti-competitive restraints and abusive practices."
"Tennis is broken," said Ahmad Nassar, Executive Director of the PTPA.
"Behind the glamorous veneer that the defendants promote, players are trapped in an unfair system that exploits their talent, suppresses their earnings, and jeopardises their health and safety."
The statement listed alleged abuses they are targeting.
It said the defendants "colluded", "fixing prize money and suppressing player earnings" forcing "an unsustainable schedule" and exploiting players financially.
The bodies show a "disregard for players" by making them "compete in 100-degree (Fahrenheit) heat, endure matches that ended at 3 am, and play with different and injury-inducing tennis balls".
The PTPA also cited image right ownership, sponsorship restrictions and the "draconian system of ranking points".
The statement also complained that tennis violates player "privacy rights".
'DIVISION AND DISTRACTION'
"Players are subjected to invasive searches of personal devices, random middle-of-the-night drug tests, and interrogations without legal representation," it said.
The ATP said that it was continuing to make change, with player input and hit back at the union.
"While the ATP has remained focused on delivering reforms that benefit players at multiple levels, the PTPA has consistently chosen division and distraction through misinformation over progress," the statement read.
"Five years on from its inception in 2020, the PTPA has struggled to establish a meaningful role in tennis, making its decision to pursue legal action at this juncture unsurprising.
"We strongly reject the premise of the PTPA's claims, believe the case to be entirely without merit, and will vigorously defend our position. The ATP remains committed to working in the best interests of the game - towards continued growth, financial stability, and the best possible future for our players, tournaments, and fans," the tour concluded.
The WTA also defended their approach to the game and said that PTPA's action "is both regrettable and misguided, and we will defend our position vigorously in due course."
In addition to Djokovic and Pospisil, the seven-member PTPA executive council also includes players, Hubert Hurkacz, Ons Jabeur, Bethanie Mattek-Sands, Taylor Townsend and Zheng Saisai.
Australian Nick Kyrgios, France's Varvara Gracheva and American Reilly Opelka have joined the PTPA's case in the United States, while Frenchman Corentin Moutet and Japan's Taro Daniel have joined the case in the United Kingdom.