Similar legislation is being pushed in the House by Rep. Jan Schakowsky, D-Ill.

"The bill is not the right vehicle to accomplish my goal," Ms. Feinstein said in a conference call convened by Health Care for America to call attention to their report. The findings indicated that health insurance industry profits rose 31 percent for the four largest health insurance companies over the last year.

Ms. Feinstein said, however, that she will continue to try to place her provision in other legislation–for example, tax legislation that Congress hopes to complete work on before the Memorial Day recess.

"I'm concerned that until 2014, there's nothing to stop these companies from raising premiums further, and this essentially would say that the
HHS secretary could assure Americans that their rates are reasonable," Ms. Feinstein said.

America's Health Insurance Plans issued a statement denying that health insurance profits are unreasonable. The AHP statement compared the 3 percent overall profit margin for the industry with that of the pharmaceutical industry, which generated a 24 percent profit margin.

The McCarran-Ferguson amendment, No. 3823, was slotted for floor action Thursday, but did not come up.

Debate continued Friday on the legislation, S. 3217, "the Restoring Financial Stability Act of 2010," but no votes were scheduled. The amendment was sponsored by Sen. Patrick Leahy, D-Vermont.

In its letter to Senate members, the property and casualty insurers said, "While the amendment targets health insurers, its flawed language and lack of definitions are a bad precedent for repealing the anti-trust exemption for any line of insurance whether it is health, life or property-casualty."

The National Conference of Insurance Legislators also sent a letter to Senate members asking them to reject the amendment.

"NCOIL legislators again reaffirm our unwavering support for McCarran-Ferguson's 1945 limited antitrust exemption, which in large part has contributed to the growth and health of our still-thriving insurance marketplace," the letter said, adding, "We strongly caution against repeal."

The letter also said, "rolling back antitrust exemptions for health insurers would ignore already-existing state antitrust protections and reduce competition while increasing costs."

The property and casualty insurers also wrote that the language in the amendment proposed by Sen. Leahy is flawed, citing a Congressional Research Office study.

"Passage of any of the measures is likely to precipitate litigation to define the scope of the prohibition and/or any remaining exemption," the CRS said in its January report.

The letter said, "Ironically, such uncertainty will likely inhibit, rather than promote competition, putting the Leahy amendment squarely at odds with the fundamental purpose of the federal anti-trust laws."

In addition, the P&C companies said, "an amendment dealing with health care issues does not belong in financial regulatory reform legislation. This amendment was specifically not included in the recently enacted health care reform legislation and should be rejected in this legislation."

Organizations signing the letter included the American Insurance Association; the Council of Insurance Agents and Brokers; the Financial Services Roundtable; the Independent Agents & Brokers of America; the National Association of Insurance and Financial Advisors; the National Association of Mutual Insurance Companies; the National Association of Professional Insurance Agents; the Physician Insurers Association of America; the Property Casualty Insurers Association of America; and the Reinsurance Association of America.