The American Civil Liberties Union of Rhode Island and the nonprofit organization Disability Rights Rhode Island, are suing the state corrections department for their alleged poor treatment of inmates with severe mental health issues.

In the class action lawsuit, filed in U.S. District court, the ACLU alleges the use of solitary confinement for inmates with mental health illnesses violates their constitutional rights and amounts to inhumane conditions.

“The significant damage that it imposes on vulnerable populations are the tragic and predictable outcomes of this intolerable and untenable situation,” said ACLU of Rhode Island head Steve Brown. “We are hopeful that judicial intervention will put an end to this disturbing state of affairs.”

In a statement, the Department of Corrections spokesman said that high-quality mental health care is guaranteed to inmates, and disputes the claims in the lawsuit.

Brown says the suit follows an investigation into the use of solitary confinement at the state’s adult correctional institutes. According to the lawsuit, 15 to 20 percent of inmates at the ACI have mental health issues.

ACLU attorney Jim Rollins says the suit seeks an end to the use of the practice for people with such illnesses.

“Change the treatment of these people who are disabled and are incarcerated in the Rhode Island corrections system. And frankly, while this isn’t a legal obligation, treated the way a society should treat people,” Rollins said.

This suit is one of several similar suits against state correctional agencies and individual correctional facilities the ACLU has filed across the country.