Most federal workers would get a one-time chance to double their retirement fund money -- with interest -- and invest it in a new noncontributory pension plan if Congress approves a substitute retirement system being considered by the White House.

The plan worked up by the Office of Personnel Management offers federal workers the chance to put up to $5,000 a year in tax-deferred accounts similar to, but more generous than, individual retirement accounts.

To finance the plan the government each year would put an amount equal to 11 percent of employes' salaries into their retirement accounts. Workers would earn interest of approximately 10 percent a year on their accounts.

As proposed, employes would pay nothing for civil service benefits, but would pay into Social Security.

The Office of Management and Budget must approve the OPM plan. Many U.S. officials say it looks almost too good to be true. Some fear the best part -- the tax-deferred investments -- could be shot down by the Internal Revenue Service. If that happened, it would be much less attractive.

Although designed as a mandatory replacement for workers who have come into government since January 1984, workers in the current civil service program could come into it with the special double-your-money incentive.

Employes who joined it would have all of the money they've invested in the federal retirement program (7 percent of salary) over their entire career doubled, with an unspecified rate of interest paid on their total amount.

That money would then go into the employes' accounts and would -- along with Social Security -- form the basis of retirement benefits. Employes could also buy the special IRAs to enhance their annuities.

At age 59 1/2 workers could withdraw all the money in their accounts, or arrange to have it paid to them as a monthly annuity. Like most other American workers, federal employes could arrange to get reduced Social Security benefits at age 62, or wait until they are 65 to draw full benefits.

Many federal workers and officials are excited by the OPM plan. Ironically, it is much less generous than a retirement package that was offered by Sen. Ted Stevens (R-Alaska) and then withdrawn because of lack of interest and/or opposition from federal unions.