The government's popular retirement-at-55 program would lose a lot of its financial glitter if the federal staff retirement system is combined with social security.

Federal and postal workers are now exempt from social security coverage (unless they earn it for non-federal work). They draw benefits from their generally superior retirement plan. They pay more -- 7 percent of total salary -- for the benefits, but their average taxable annuity is nearly triple the average tax-free social security payment. And federal workers can, and do, retire much earlier than most private industry employes because of the way their program is structured.

Currently, about one-third of all eligible federal workers retire at age 55, according to government statistics. It is possible in some circumstances to retire (on reduced annunity) at age 50 with 20 years service, or even as early as age 43 if the employe has 25 years service and his/her agency is undergoing a reorganization or a layoff.

But under the proposal to coordinate civil service retirement programs with social security, federal workers retiring at age 55 would receive less under the combined system than they would under straight civil service retirement. Their combined benefits would, in many cases, be better at age 62 -- but the lure of earlier retirement would be less attractive.

Examples: Take the case of a worker retiring today, with 30 years service at age 55. Compare his/her current benefit with the same payout under combined social security-civil service. Here goes:

The employe retires now, under the current civil service system, at age 55. His final salary is $10,000. That employe's before-taxes annuity would be $5,260 per year.

The same employe retires today at 55 undercombined civil service-social security. He would get nothing from social security at age 55, and $4,630 from civil service. At age 62 the retiree's payment from civil service would drop to $3,200 and he would begin drawing social security (taxfree) of $3,270. Total income from both plans would be $6,470 at age 62.

The employe retires now with a $20,000 salary. Under civil service he would get an annuity of $10,520 at age 55.

That same employe, retiring undercombined social security-civil service, would get $9,260 from civil service and nothing at age 55 from social security. At age 62 the retiree's civil service payment would drop to $7,220 and he would begin getting $4,660 (tax free) from social security. His combined annuity would then be $11,880. But again the employe would not get the full double benefit until age 62.

The $30,000-a-year employe retires. Present annuity from civil service would be $15,780 before taxes.

That same employe, under the combined plan, would get $13,890 from civil service at age 55. At age 62 he would begin geting $5,250 from social security, but his civil service benefit would drop to $11,580. Total from both would be $16,830 with the social security portion tax-free.

The $50,000-a-year employe retires from government at age 55 under today's rules. His annuity would be $26,300.

Under combined civil service-social security, the employe would get a federal annuity of $23,150. At age 62 the civil service benefit would be reduced to $20,800 and social security would begin paying him/her $5,400. The total benefit at age 62 would be $26,200, or $100 less than the amount that retiree would be due now, at age 55, under straight civil service. The tax benefit from social security would offset that.

But do federal workers want to wait those extra years for the benefits?

Within the next few weeks Congress will begin to consider proposals to require federal workers to come in under social security. In general, lower-salaried federal workers would be slightly better off under the social security-civil service combination. Higher paid personnel ($25,000 and above) would get a benefit reduction of about 5 percent.

But one of the important aspects of the combined systems would be the financial disincentive to early retirement. If you like the idea of retiring before 62, it is something to consider.