BOISE - A private prison company has asked a federal judge to bar a lawsuit brought by 24 inmates and the American Civil Liberties Union over violence at Idaho's only private prison, saying the primary plaintiff should go it alone in court.

Corrections Corporation of America runs Idaho's only private prison, the Idaho Correctional Center near Boise.

Inmate Marlin Riggs brought sued the Nashville, Tenn., company last year over violence at the prison.

The ACLU filed an amended complaint in March on behalf of Riggs and the other inmates, saying the facility is so violent that it's known as "gladiator school" and that guards deliberately expose prisoners to brutal beatings from other inmates.

In its response filed with Boise's U.S. District Court last week, Corrections Corporation of America says the amended lawsuit oversteps limits the court set when it agreed to appoint attorneys to help Riggs bring his case. The company also contends that the amended lawsuit is unduly prejudicial.

"This court should not allow the class to piggyback their class claims onto Riggs' original complaint because Riggs lacks the standing to represent the class," the CCA attorneys wrote in their motion. "It will also prejudice the CCA defendants at trial where the jury will not only decide liability on Riggs's claims, but still hear evidence relating to the class allegations."

If the ACLU and the other plaintiffs want to file a class-action lawsuit against CCA, they should do that separately, CCA's attorneys contend.

The ACLU responded in a court document Thursday, contending that plaintiffs frequently file amended lawsuits expanding the scope of the case and adding new plaintiffs. Besides, the ACLU said, it's Riggs' decision - not CCAs - whether he wants to bring a case by himself or on behalf of a class. And while the ACLU agrees that the corrections company could suffer some prejudice because of the expanded claim, the attorneys say it's in line with the prejudice suffered by any defendant in any expanded lawsuit, and it's not unduly prejudicial.

Riggs and the ACLU are suing for $155 million in damages - the entire net profit of the Corrections Corporation of America for 2009. The inmates claim in part that guards force prisoners to turn each other in for violating prison rules, and those who refuse are moved to cell blocks where they are surrounded by enemy gang members and face certain beatings. The inmates also contend the prison denies injured inmates medical care to save money and hides the extent of injuries.

CCA officials have countered that the prison is under the constant supervision by the Idaho Department of Corrections and that it meets the highest professional standards in the country for correctional management.