Judith Havemann asserts that the 97 percent of federal employees now covered under the civil service retirement system who have chosen not to switch to the new federal employees retirement system "are probably making a big retirement mistake" {Financial Planning section, Nov. 15}. In fact, it is Congress that made a "big retirement mistake" in trying to save money by creating a system that unrealistically relies on a do-it-yourself savings program.

Instead of providing an adequateemployer-paid pension program to supplement federal workers' Social Security payments, Congress opted for a minimal pension program supplemented by a generous voluntary savings plan. For high-income employees and some "second earners," an emphasis on voluntary savings for retirement may make sense. They can benefit from tax breaks for the money they put into the savings plan and take full advantage of matching contributions made by the government.

But the FERS savings plan offers little to low- and moderate-income federal workers who have no money to spare from their paychecks. It gives them only a yearly government contribution of 1 percent of pay. Those who can afford voluntarily to save for retirement will typically be able to do so only after their housing and children's educational needs have been met, when it will be too late for them to accumulate a realistic retirement nest egg.

Some federal workers in the lowest pay grades, particularly those with many years of Social Security coverage, may do better under FERS than under CSRS even without savings plan contributions simply because Social Security benefits are tilted in favor of lesser earners, but others will not.

Current CSRS members are fortunate in being able to protect themselves by staying under the present system if it better suits their financial needs. New federal workers do not have that protection.

It is time for Congress to take a hard look at FERS and consider replacing its reliance on voluntary savings with an adequate employer-paid pension program.

KAREN W. FERGUSON Director, Pension Rights Center Washington