Health Republic Insurance Company of Oregon, a Lake Oswego-based insurer that is phasing down its operations, on Wednesday filed a $5 billion class action lawsuit on behalf of insurers it says were shorted by the federal government under an ObamaCare program.

The lawsuit, filed in the United States Court of Federal Claims, focuses on a program that was intended to offset insurer losses in the early years of the implementation of the Patient Protection and Affordable Care Act.

Instead, payments to insurers under the “risk corridor” program amounted to 12.6 percent of the amount expected for 2014, and are expected to be similarly low for 2015.

Federal law and regulations “are unequivocal about the payments the Government must make,” according to the lawsuit. “The law is clear: the Government must abide by its statutory obligations.”