PORTLAND, Ore. -- Regence BlueCross BlueShield of Oregon this week raised rates by 26 percent for individual insurance plans due for annual renewal and by 16 percent for small group plans.

The sharp increase led a Portland woman to file a challenge of the rate hike with the state. Department of Consumer and Business Services officials said they will schedule a hearing to determine whether the increase is justified, The Oregonian newspaper reported.

Dr. Bart McMullan, president of Regence BlueCross, said the rate increase is necessary because his company lost $21 million to $23 million last year on its individual health care plans.

"The last thing we want to do is raise premiums for individuals by 26 percent," McMullan said. "We are sorry we have to do it. We want to work on the causes so we don't have to do this over and over."

Regence BlueCross insures about 89,000 of the 246,000 Oregonians with individual plans and about 37,000 of the 252,000 residents in small group plans, which are mostly for small businesses with 50 employees or fewer.

More than 1 million Oregonians are insured by large employers.

The state only regulates rate increases for individuals and small groups said Cory Streisinger, director of the Department of Consumer and Business Services.

"Our responsibility is to look out for the interests of Oregonians in making sure that rates are fair in relation to the benefits they receive, but we also have to be sure that insurance companies can stay in business," she said. "A 26 percent increase is a very substantial increase. We as a state and a society need to get a handle on health care costs."

Most of Oregon's largest insurers have been raising rates by double digits annually over the last two years.