Marring the excellent editorial {Nov. 23} opposing the Reagan administration's counterproductive "Mexico City policy" regarding international family planning assistance programs involved in "abortion-related activities" was the totally incorrect statement that a similar family planning "controversy has been settled domestically." President Reagan on July 30 directed the Department of Health and Human Services to impose the Mexico City policy on domestic family planning programs funded under Title X of the Public Health Service Act.

The proposed regulations, known as the "Gag Rule," not only would control public funds but would prevent a family planning clinic from using its own private funds for legal and appropriate medical care, including counseling and information about abortion. If implemented, the Gag Rule would put Title X recipients out of business and would effectively kill or hopelessly cripple the program. Most important, it would make high-quality reproductive health care unavailable to millions of poor women.

The Gag Rule is opposed by 32 state governments; by the deans of all 25 U.S. Schools of Public Health; by more than 70 national organizations including the American Medical Association, the American College of Obstetricians and Gynecologists, the American Public Health Association, the Child Welfare League and the National Council of Churches; and by more than 150 members of Congress. The Senate has approved a provision in the funding bill for DHHS that would prevent the department from implementing the Gag Rule.

The Gag Rule is unconstitutional, violating the First Amendment and the privacy rights of clients and providers of family planning services. It contravenes federal court rulings, undermines state laws, is unreasonably broad and threatens the lives of poor women.

As the national organization representing these women and the entire community of family planning providers, the National Family Planning and Reproductive Health Association will soon file suit in federal court to overturn the Gag Rule. We will win, and the Gag Rule will no longer exist. SCOTT R. SWIRLING Executive Director, National Family Planning and Reproductive Health Association Washington

A Nov. 23 editorial criticized the administration's "Mexico City policy," which denies U.S. population-control funds to private organizations that "perform or actively promote abortion as a method of family planning in other nations."

The Post asserted that the Planned Parenthood Federation of America cannot accept the policy "because PPFA works with indigenous health and family planning groups in many countries where abortion is legal, {and} it cannot guarantee that ultimate subcontractors will not use their own money for these {abortion} services."

It is nonsense to suggest that PPFA "cannot guarantee" that its foreign subgrantees eschew abortion. According to the Agency for International Development, 800 family planning agencies in 70 nations -- including the Planned Parenthood for Latin America -- have accepted U.S. funds under the Mexico City policy.

PPFA will not join these organizations because PPFA is committed to the doctrine that abortion is an essential component of all population-control efforts. As PPFA President Faye Wattleton put it in a speech to the National Press Club April 14, legal abortion is "a universal human right, to which every person on this planet is entitled. . . . Our government must increase its funding to make contraception and safe, legal abortion available in developing nations."

However, according to the United Nations, in all except eight of 126 "less developed" nations, abortion for social reasons is against the law. These anti-abortion laws generally reflect the religious and cultural values of the peoples of these nations. PPFA and its overseas surrogates are determined to undermine these laws, and that is the real reason why PPFA refuses to conform to the Mexico City policy.

The Post cited "a study done at the University of Michigan School of Public Health," which projected that a cutoff of AID funding to PPFA would result in 69,000 additional abortions over a three-year period. The Post neglected to mention that this "study" was commissioned and paid for by PPFA. Among other defects, the study failed to consider that if PPFA succeeds in undermining the anti-abortion laws of even a few less developed nations, the result will be an increase in abortions far greater than the 69,000 projected. Subsidizing PPFA to diminish the number of abortions makes as much sense as subsidizing the Mafia to curb the smuggling of illegal drugs. DOUGLAS JOHNSON Legislative Director, National Right to Life Committee Washington