Allowing insurance agents to offer discounts on commissions could save consumers billions of dollars a year, supporters of a measure to remove restraints on such discounts said yesterday.

Despite variations in overhead costs and levels of efficiency among insurance agents, "statutes in all 50 states require that each and every one of those agents must charge precisely the same commission as every other agent for a particular policy," said Rep. John J. LaFalce (D-N.Y.), said at a hearing of the House small-business subcommittee. Commissions are set by companies and may not be reduced by the agent under state laws.

LaFalce has introduced a bill that would nullify laws that prohibit agents from offering rebates on commissions to attract buyers. The LaFalce bill would repeal an exemption from antitrust prosecution for such laws which "may very well be one of the most costly and enduring price fixing schemes ever perpetrated upon the American public," LaFalce said.

The measure is opposed by insurance firms and insurance agents who said yesterday that the practice is not price-fixing. They said that allowing agents to compete with lower prices would also allow agents to discriminate among customers who should be offered insurance under equal terms and would make it harder for consumers to compare policies.

Testifying in favor of the measure, Wisconsin's commissioner of insurance Susan Mitchell said the current system provides an incentive to an agent to sell consumers a higher-priced product than the consumer needs, sometimes because commissions are built in to premium costs.

The proposed change in the law "is a rather simple idea to reduce regulation and increase competition," she said. Mitchell compared the proposal with the repeal by Congress of the fair-trade laws that required re tailers to sell certain products at the price listed by the manufacturer and deregulation of stockbrokers' commissions.

Proposed legislation similar to the LaFalce bill has been introduced in the Wisconsin legislature at Mitchell's request, she said.

Ralph Nader testified in support of the bill and called for an end to state rules that prohibit groups of consumers from banding together solely to get cheaper group rates on insurance.

If increased competition resulting from the proposed change in the law lowered commissions by only 10 percent, "there would be savings of $2 billion for American consumers," Nader said.

LaFalce said the savings might range from $5 billion to $12 billion, using an estimate from an insurance agents' association study.

Julius Vogel of the American Council of Life Insurance challenged claims that the proposed change would benefit consumers. "Indeed, we believe it would lead to unfair rate discrimination, diminished competition and higher prices," he said.

The LaFalce proposal "will produce unfair discrimination among purchasers of life insurance," said William N. Albus, associate general counsel of the National Association of Life Underwriters. "The antirebate statutes have effectively protected the consumer through an orderly pricing structure," he said.