Members of Congress anxious to blend the civil service retirement system with social security could deal their own juicy pension plan a heavy financial blow in the process.

Congress is considering recommendations of a blue-ribbon panel on how best to integrate the two systems. Most American workers are required to contribute to social security, the Congress is looking for ways to cut back their social security tases. Adding 6 million uncovered federal, state and local government workers (with their generally higher incomes) to social security would help, some people think. Members of Congress, incidentally,are exempt from social security although they write the laws that govern it.

Comparing the two systems is difficult because they are intentionally different. Civil servants pay more for their benefits, which are much, much higher than anything possible under social security. Federal workers pay taxes on their annuities once they have gotten back everything they contribute to the civil service fund (that usually takes about 18 months). t

Civil service pensions are based on length of service and salary. You get what you paid for, and what you earned. Social security is a semi-welfare system that features "income distribution" -- meaning that you get back proportionately less, based on what you earn and pay into the system.

Members of Congress enjoy the best of retirement worlds, using a super-rich version of the civil service retirement program. They pay slightly more for it, but no member of Congress (with a few terms under his belt) ever has to get by on the $296.96 per month that social security recipients average. The typical civil service benefit today averages $848 per month. Retired congressmen do better still.

Some differences between the two systems:

There are about 3,500 retired federal workers whose monthly annuities (before taxes) are more than $3,000. All of them are former members of Congress or recently retired high-level career officials.

Federal workers can (in "reduction inforce" situations) retire as early as age 43 on sharply reduced pensions, or at 55 with no loss of annuity. About one out of every three eligible federal workers now retires at 55. Under social security, reduced benefits do not begin until age 62. Full benefits aren't available until 65 and only if one retires at that age.

Many federal workers and retirees defend the civil service retirement system on the ground that they pay taxes on their annuities (after getting back what they paid in) while social security benefits are taxfree. True, but so what? In the first place, the days of tax-free social security benefits seem to be numbered. Second, the lowest social security benefit is $122 per month, the maximum is $572 and the average is $292.96. By contrast, the average federal retirement benefit today is $848 per month. Given the choice, most people would rather pay taxes on $848 per month than get $292.96 tax-free.

The Office of Personnel Management say that only 10 percent of all federal retirees (not survivors) have annuities of under $300 a month. That is still a few dollars mor than the average social security monthly benefit.

Social security provides more comprensive benefits to survivors and better short-term disbility benefits and vesting than the civil service program.

Social security benefits are adjusted once a year, in July, for inflation. Civil service benefits are adjusted every six months, March and September, for inflation.

One reason many federal workers joined the federal government was for its superior retirement system. Many think the government would be guilty of breach of contract if it changed the system now.

The two systems are a long way from becoming one. Congress must approve a merger, and it is preoccupied with many other things this year. Legislation has been introduced to force members of the Senate and House to join the social security system. Watch this space to see how the legislators like the idea of joining the social security system, once they figure out what it will do to their prospective pensions.