WASHINGTON—Concern is growing on Capitol Hill and beyond over the Obama administration's delay in filling two key insurance-related positions established by the Dodd-Frank Wall Street Reform and Consumer Protection Act.

A bipartisan group of lawmakers sent a letter last week to President Barack Obama and Treasury Secretary Timothy Geithner concerning the issue. Led by Reps. Ed Royce, R-Calif., and Jim Himes, D-Conn., the group noted that the financial services reform law creates a Federal Insurance Office within the Treasury Department, and that the FIO director and an insurance expert are to serve as members of the Financial Stability Oversight Council.

“While we appreciate the size and the scope of the implementation task before you, we are concerned that, six months after enactment, the positions of the FIO director and the council's insurance-designee remain unfilled,” lawmakers said in the letter.

Other lawmakers, including one of the principal architects of the financial services reform bill—Rep. Barney Frank, D-Mass.—have asked that the FSOC postpone decisions regarding the insurance industry until its representatives have been appointed to the panel.

The council has the power to determine that nonbank financial companies—including insurers—present systemic risks to the economy and must be subject to heightened supervision. Insurers, however, have argued that they don't present systemic risk.

The presidentially appointed member with insurance expertise would be one of 10 voting members of the council, and the only one not heading a federal agency. The FIO director, and an already designated representative of state insurance regulators, would serve as a nonvoting council adviser.

President Obama has yet to appoint the insurance expert and no one has been nominated to head FIO. John M. Huff, director of the Missouri Insurance Department, represents state insurance regulators on the council.

The FSOC recently sought comments on proposed criteria that regulators would use to determine whether a nonbank financial company poses a systemic risk.

The Risk & Insurance Management Society Inc. “is continuing to focus and support the development of a Federal Insurance Office,” said John R. Phelps, RIMS secretary and board liaison to the external affairs committee.

“We recognize the benefits for large commercial companies; we know it's a process to get there,” said Mr. Phelps, who also is director-business risk solutions at Blue Cross and Blue Shield of Florida Inc. in Jacksonville. “It's not something that's a matter of waving a magic wand. Our most fervent hope is that the leadership for that office will be people who are experienced and have a thorough understanding of the insurance and risk management industry.”

“The whole debate is very useful in underscoring the big point that we have, which is that insurers are distinctly different from other financial services institutions,” said Leigh Ann Pusey, president and CEO of the American Insurance Assn. in Washington.

Appointing the insurance industry members is “critically important because we are in a regulatory design phase,” Ms. Pusey said. “Having someone in that process with an insurance perspective is critical.”

Jimi Grande, senior vp in the National Assn. of Mutual Insurance Cos.' Washington office, said NAMIC has “much greater concern with the absence of the insurance expert on the FSOC than we do getting FIO up and running.”

He said Congress made it clear in Dodd-Frank that lawmakers did not believe insurers pose a systemic risk.

“With a room largely filled with banking regulators, it will be easy for them to try a one-size-fits-all approach and snare insurers into their jurisdiction,” Mr. Grande said.

The Property Casualty Insurers Assn. of America “remains very concerned that the FSOC is working on extremely important issues relating to determinations on systemic risk without two of the three insurance representatives in place,” David Sampson, president and CEO of the Des Plaines, Ill.-based group, said in an e-mail.

“The FSOC has now met three times without the benefit of insurance expertise,” Mr. Sampson said. “During the last FSOC meeting, deliberations began over a proposed rule for nonbank financial institutions that could affect insurers. We continue to urge the White House and Department of Treasury to appoint the insurance expert and the FIO director promptly so that the FSOC implications for the insurance sector be appropriately considered.”

“I certainly agree with the Royce letter,” said Joel Wood, senior vp of the Council of Insurance Agents & Brokers in Washington. “They'll get it filled and this shall pass,” he said.

“In the meantime, I know there is extreme anxiety among insurers about the lack of insurance expertise while decisions are being made about what constitutes a systemically risky company. There will be much greater long-term value as well from the FIO, so we're anxious to see that filled,” Mr. Wood said, expressing confidence that the administration would choose “very competent individuals.”