Comment letters on the U.S. Department of Labor's proposed fiduciary rule poured in Tuesday, the last day of the comment period, with many groups representing retirement plan investment and service providers warning that while they support a standard that protects clients' best interests, new rules to ensure that in specific situations would be unworkable.

Others, like the ERISA Industry Committee, which represents large employers on benefits issues in Washington, said in its letter that more changes were needed to avoid increasing regulatory burdens, costs and uncertainty among plan sponsors, plan participants and service providers. ERIC called for the DOL to be clearer about which employees of a plan sponsor can offer investment advice to other employees.

Hearings will be held the week of Aug. 10.

The Securities Industry and Financial Markets Association's asset management group said in one of eight letters submitted by the group that its members already are fiduciaries when they act as discretionary investment managers or provide investment advice to employee benefit plans subject to ERISA, but the proposal “will restrict asset managers' ability to provide information” and services. Money managers and investors deemed sophisticated “will be burdened by standards designed for retail retirement savers,” and “plan performance may suffer, as asset managers and their offered products become restricted,” the SIFMA group letter said.

“We agree with the DOL that more can be done to help Americans save for retirement and that there should be a best interests standard in place,” said Kenneth E. Bentsen Jr., SIFMA president and CEO, in a statement. He added, however, “we believe DOL is the wrong regulator to be in the lead here and the rule as written completely misses the mark.”

In its letter, the CFA Institute said that despite concerns raised by some industry participants about potentially limited service to some parts of the retirement investment market, the institute “believes the proposal does a good job of accommodating various business models while still requiring investment service providers to act in their clients' best interest … Action in favor of a higher standard of care among those providing personalized investment is long overdue.”

Labor Secretary Thomas Perez defended the proposed rule Tuesday during a Senate Health, Education, Labor and Pensions Subcommittee on employment and workplace safety hearing. “The problem in our system is that (the current system) incentivizes complexity … because complexity generates more fees.”

Hazel Bradford writes for Pensions & Investments, a sister publication of Business Insurance.