A lawsuit filed in federal court in Camden on Monday alleges that the American Osteopathic Association illegally requires doctors of osteopathic medicine to buy membership in the Chicago organization in order to be board certified.

The 23-page lawsuit, filed by attorneys at Duane Morris L.L.P., seeks class-action status. It says the class is comprised of more than 32,000 doctors of osteopathic medicine who have board certifications through the American Osteopathic Association.

The full price for an annual membership is $683. In the year ended May 31, 2014, membership dues accounted for $20.4 million of the association's $44 million in revenue, according to its latest public tax return. The association had $7.6 million in revenue from certifying boards.

"There are no procompetitive justification, medical justifications or other justifications for the AOA's requirement that [doctors of osteopathic medicine] buy annual membership in the AOA in order to maintain their board certification," the suit claims.

AOA chief executive, Adrienne White-Faines, said that the membership policy is under review, but also that "AOA board certification services are legally appropriate as a benefit of membership."