ALBUQUERQUE — A major insurer on the New Mexico health exchange is not budging from a proposal to raise its premiums for some customers by more than 50 percent.

Blue Cross Blue Shield of New Mexico had until this month to revise its filing with the state insurance office for a 51.6 percent increase. The request was first issued back in April.

The hike reflects the actual costs of coverage instead of the projections used when it first set rates, Blue Cross Blue Shield President Kurt Shipley said.

Superintendent of Insurance John Franchini said his office plans to look into why Blue Cross’ request is so much bigger.

“They seem to have a difference of opinion,” Franchini said. “We’re asking a lot of questions.”

Franchini’s office will rule on the request from Blue Cross and the other insurers on the exchange at the end of July, the Albuquerque Journal reported Friday. The insurance companies can request a hearing after that time.

The state exchange offers plans by five different insurance companies. Three have filed requests to boost premiums between 2 and 17 percent, depending on the plan. New Mexico Health Connections is seeking between 4 percent and 17 percent. The company said the type of plan chosen by the customer as well as where the customer lives would be factors. Presbyterian Health Plan has asked for a 6 percent increase. Molina Healthcare of New Mexico wants an average of 2 percent raise.

CHRISTUS Health Plan, however, is not seeking an increase.

New Mexico Health Connections CEO Martin Hickey said health plans and their costs are inherently complex. The costs for some plans for some customers will be higher but others will have lower costs, he said. Accompanying deductibles will be different depending on the plan.

“In most cases, we are trying to keep rate increases as low as we can,” Hickey said.

Insurance premiums are determined by several factors such as age, smoking habits and level of coverage. According to an analysis by the Journal of this year’s rates, a 50-year-old non-smoker living in Albuquerque would pay a monthly premium of nearly $200 for Blue Cross’ lowest-priced, “bronze”-level plan. That is more than New Mexico Health Connections, which would charge around $182, but below the other three insurers. Their cheapest “bronze” plan costs $365.25 a month.