Utah’s latest attempt to curb soaring health care costs may have the unwanted effect of reducing competition among health insurers.

Insurance broker and Taylorsville Republican Rep. Jim Dunnigan has revived a vetoed bill that would grant health insurance companies greater flexibility in pricing their plans for small employers. The bill would allow insurance companies to extend discounts to young workers and single parents with one child, while hiking premiums for older workers and larger families.

It was unanimously endorsed last week by the Business and Labor Interim Committee and is expected to surface in a special legislative session on June 15, said Dunnigan, who expects little opposition. “I think we’ve addressed everyone’s concerns,” he said.

Everyone, that is, except the country’s largest health insurer, UnitedHealthcare, which has threatened to pull out of Utah’s small-group market if the bill passes. The company initially denied any threatened exodus through spokeswoman Cheryl Randolph. But at an Utah Insurance Department board meeting on Tuesday, a United representative said the programming costs of adding a special pricing category for single, one-child parents may leave the company with no choice but to bow out.

United is working with Dunnigan to keep coverage affordable for small businesses and is committed to the small-group market in Utah, Randolph added in a later statement.

Under current law, insurers charge a parent with one child the same premium as a parent with two or more kids.

Dunnigan said he is negotiating with United and is confident he will find a solution. “If they pull out of the market, it will be for another reason,” he said.

United and other big national carriers have fought to grab a bigger share of the Utah market, where Selecthealth and Regence BlueCross BlueShield claim 60 percent of all privately insured residents.