Updated

Sen. Ron Johnson is suing to stop the government from paying most of the medical insurance premiums for members of Congress and their aides now required to obtain coverage through the new health care law's state exchanges.

The Wisconsin Republican filed a suit Monday in U.S. District Court in Green Bay, Wis., challenging a September ruling by the Office of Personnel Management. The agency ruled that lawmakers and their staffs should continue getting health care benefits covering 75 percent of their premium costs after leaving the health insurance program for federal workers.

Johnson says the lawsuit is about ensuring that Congress receives no special treatment under President Obama's health care overhaul. The exchanges were set up for people who don't get health coverage through employers.