Reagan administration officials say a proposed federal retirement system offering workers tax-deferred investment programs and an optional $5,000 individual retirement account will get speedy consideration by the White House.

The Office of Personnel Management's proposed plan would become mandatory for employes hired since 1984 and optional for other civil servants. But it must be cleared by the Office of Management and Budget before it can be approved by the White House and introduced as legislation.

As proposed, federal and postal employes who are now covered by Social Security would not have to pay for their retirement benefits. Agencies would set aside an amount of money equal to 11 percent of workers' salaries each year into interest-bearing accounts. That 11 percent contribution would not be taxed as income until workers retired and started drawing it. It is similar to retirement programs that have been established by many companies.

In addition, employes could invest up to $5,000 of their own money annually as tax-deferred savings to supplement retirement income.

Congress has until the end of this year to come up with a pension plan for workers hired since January 1984. Those employes now contribute only 1.3 percent of their salaries toward the federal retirement program and about 7 percent for Social Security.

Workers hired before 1984 are covered by the federal retirement program (and put 7 percent of their salaries into the fund) but pay only the Medicare portion of Social Security. Those workers would elect to stay in the present civil service retirement plan or come into the new system, if Congress approves it.

The biggest drawback to the OPM plan could be the Internal Revenue Service. The proposed $5,000 super IRAs for federal employes would be more generous than those available to most private workers, and could cut into tax revenue.