CONCORD, N.H. — A legislative committee on Tuesday rejected a key part of a plan designed to prevent the collapse of New Hampshire’s individual health insurance market.

With continuing uncertainty in Washington, some premiums under the federal Affordable Care Act are expected to increase next year by more than 40 percent in New Hampshire.

The state insurance department has been working on a plan to offset those hikes through a “reinsurance program” that would create a pool of money to reimburse insurers for high-cost claims, theoretically allowing them to lower their rates. The department wanted to pay for the program with federal money and a fee imposed on insurance companies.

On Tuesday, the Joint Health Reform Oversight Committee authorized the department to seek a federal waiver for the plan but not the fee on insurance companies, which Republican Gov. Chris Sununu said amounted to a tax increase.

“It is wrong to create an additional assessment on the backs of Granite Staters who are already struggling to pay exorbitant health care costs,” Sununu wrote to the committee. “New Hampshire will not move forward with a waiver that increases health care costs, or makes it harder to attract or retain workers.”

About 98,000 individuals in New Hampshire are covered through the state’s federally facilitated Obamacare marketplace; about 43,000 of those are Medicaid recipients. Among the non-Medicaid recipients, the average monthly premium this year was $399, though nearly two-thirds of the individuals receive subsidies or tax credits, dropping the average to $242.

Nothing is final yet, but three companies — Ambetter from New Hampshire Healthy Families, Anthem and Harvard Pilgrim — have submitted preliminary pricing information to offer individual plans next year. Sununu asked them on Tuesday to “immediately disclose if they are in or out of the individual market and what a plan would look like,” but they have until Aug. 16 to submit final details.

According to information released Tuesday by the federal government, insurers have requested rate increases ranging from less than 1 percent to just over 45 percent. The insurance department says a 40-year-old non-smoker who chooses a “silver-level” plan would face a monthly premium of $479, a 43 percent increase over 2017.

The insurance department had planned to hold two public hearings, in Concord on Wednesday and Lebanon on Thursday, about its reinsurance plan. But after the committee’s vote, the department said the meetings would be postponed until “there is more clarity about the specifics about the state’s approach.”