CHATTANOOGA, Tenn. (AP) - BlueCross BlueShield of Tennessee has proposed raising premiums next year by an average of more than 36 percent after losing $141 million during its first year of offering individual health plans through the federal Affordable Care Act. The state’s biggest health insurer said it initially underestimated the number and cost of the medical claims filed by new enrollees, the Times Free-Press reports. BlueCross Vice President Roy Vaughn said the insurer’s mission was to serve the entire state as affordably as possible under the Affordable Care Act. “It was a new market, and as we filed our initial rates for 2014 we had no data on the population that we would cover. We did not foresee the kind of medical costs that we’ve experienced with this group of members,” Vaughn said. The insurer enrolled nearly two-thirds of the 231,000 Tennesseans who signed up for health insurance exchange plans last year. Walter Davis, executive director of the Tennessee Health Care Campaign, urged state regulators to take a hard look at the proposed rate increases to make sure they are justified. “The number of Tennesseans who are uninsured is going down and more people are getting preventive care, rather than going to more expensive emergency rooms when they get sick,” he said. “That should help hold down costs and ultimately benefit everyone. But it may take some time since some of those getting coverage for the first time may be catching up for a lack of care in the past.” Kevin Walters, communications director for the Tennessee Department of Commerce and Insurance, said state regulators “will examine everything these health insurers give to us” before making a decision by the Aug. 25 deadline. “This is something we take very seriously for the consumers of Tennessee and we plan on scrutinizing each of these proposals,” he said. If the proposed rate hikes are approved, average individual rates would rise to more than 60 percent above their 2014 levels.