Government workers and retirees would get a voucher eachyer to buyhealth insurance under a legislative proposal being prepared by the Office of Personnel Management.

Backers of the plan say that in many cases the checks could cover the entire cost of insurance premiums. But opponents say the plan is a trap that could leave cost-conscious feds open for big bills if major illness struck their families.

The proposal, which must be cleared by the Office of Management and Budget and approved by Congress, could not go into effect until 1987 at the earliest.

Federal workers now pay a portion of their health insurance premium, no matter which of the 210 plans they select. Each plan offers family and self-only coverage.

But many also offer low or high options. The latter usually cost more because they provide better benefits or have lower deductibles and co-insurance requirements. Although the government pays 61 percent of the average premium, workers and retirees still must shell out between $300 and $1,500 a year on their own.

Under the voucher system -- a "reform" long sought by the administration -- each of the nearly 5 million civil servants and retirees would get a voucher every year to cover health insurance. If they could find a plan that cost the same as the voucher, or less, their premiums would cost them nothing.

Two kinds of vouchers, one for single coverage and one for family plans, would be offered. No word yet on the big question: how much would the insurance check be worth?

If the Senate gets its way, the voucher plan could be incorporated in a compromise congressional budget package. If not, separate legislation to make the vouchers a reality will be introduced later this year.