The Association of American Physicians and Surgeons has asked a federal judge to stop the Texas Medical Board from accepting anonymous complaints.
The group claims the regulatory board has used anonymous complaints to intimidate and retaliate against doctors.
The lawsuit was filed Friday in federal court in Texarkana.
It also alleges conflicts of interest and privacy breaches by board members and expert witnesses hired by the board.
Board officials defended their record at an October legislative hearing and said the anonymous complaints protect whistle-blowers from retaliation. They said less than 2 percent of complaints are anonymous.