WHEN FEDERAL EMPLOYEES say they gave at the office, do they realize where some of their one-fund contributions may be going? This year's list of eligible charities approved for financing from the Combined Federal Campaign includes some far-reaching definitions of "health and welfare" agencies. Somehow we never quite thought of the National Rifle Association's subsidiary, the Firearms Civil Rights Legal Defense Fund, as one of your basic health and welfare service providers. NRA general counsel Mike McCabe told Post staff writer Mary Thornton that this fund is to "represent people who have been improperly handled civilly or criminally in the context of firearms laws." Some worthy cause.

Equally out of place in the Combined Federal Campaign list is the National Right to Work Legal Defense Fund, defended in this case by spokesman Clayton Roberts: he says the fund qualifies as a "health and welfare" charity because it "is a legal aid group giving assistance to individual employees who are victimized by compulsory unionism." A bit of a stretch, you might conclude.

It isn't a matter of political right or left, either. This issue first arose during the Carter administration, when all sorts of advocacy groups were allowed into the federal one-fund campaign, among them the Puerto Rican Legal Defense Fund, the NAACP Legal Defense and Educational Fund, the Sierra Club and the Indian Law Resource Center.

Whatever your opinion of the merit of what these organizations do, they do not command the kind of widespread support that goes to the more traditional charities. That can hurt the long-term success of what is a taxpayer-supported campaign using public facilities. The purpose of the Combined Federal Campaign has been to provide a convenient, low-overhead way for federal workers to give to agencies that work directly to help people in need -- organizations that are more hard-pressed than ever.

Many federal employees may prefer either to give to the United Way, which does not include these advocacy groups, or to designate their CFC contribution to the charity of their choosing. In the meantime, there is relief in sight for the CFC: Constance J. Horner, director of the Office of Personnel Management, has said she will change eligibility rules next year to exclude legal defense funds and lobbying groups. That should go a long way toward restoring federal employee confidence in an important philanthropic effort.