Federal employes who now pay several hundred dollars a year for "low option" health insurance would not have to pay any premiums, according to Reagan administration officials, under a voucher insurance plan that is awaiting clearance at the Office of Management and Budget.

The voucher plan is the idea of the Office of Personnel Management. OPM handles the Federal Employee Health Benefits Program (FEHBP), approving rates and benefits for 130 participating plans.

FEHBP is the nation's largest "company" health plan. It covers 10 million civil servants, family members and retired government employes.

About half the people in the Washington area are covered by the program. Depending on the option (high or low) and plan they choose, employes' premiums range from $300 to $1,200 a year.

Under the voucher system, which would have to be approved by Congress, the government would give each employe and retiree a voucher for a fixed amount of money to be used to purchase health insurance. OPM says vouchers would cover all of the premium if employes chose a low-option plan. Workers who wanted high-option plans, which provide greater coverage, would have to pay the difference out of regular biweekly payroll deductions.

Presently the government share of health premiums is based on a complicated formula established years ago by Congress. The federal payment is set at 60 percent of the average premium charged by the so-called Big Six carriers in the program.

Plans whose premiums are considered in setting the formula are Blue Cross-Blue Shield; Aetna; Kaiser of Northern California; Kaiser of Southern California and the National Association of Letter Carriers and the Mail Handlers Union. Under this complicated formula system the actual government payment to an individual employe's health plan ranges from 40 percent to 75 percent of the total premium.

Administration officials who support the voucher system--it must be okayed by the OMB before it goes to the White House cabinet counsel--say it would save many employes, and the government, money. They feel it would encourage carriers to construct plans that would be covered by the voucher, and would encourage many employes to avoid high-option plans whenever possible.

Opponents of the system, including many House Democrats, maintain that the voucher system would force employes to buy low-option plans, which would not provide them with the protection offered by more costly plans.

Even if the plan was approved this year it would be 1985 at the earliest before the government could put it in practice.

OPM is in the midst of contract negotiations with carriers now to determine what premiums and benefits will be offered by the FEHBP next year. Although benefits have been reduced over the past two years, premiums have jumped more than 50 percent. The new premiums and benefits (for the 1984 insurance year) will be announced this fall. There will be an "open season" later this year when employes and retirees will pick their 1984 health plans.