A group of clergymen and scholars has proposed a constitutional amendment defining marriage as "a union of a man and a woman," an effort a critic termed "the nuclear bomb" of anti-gay measures.

The proposed amendment by the Alliance for Marriage states: "Marriage in the United States shall consist only of the union of a man and a woman. Neither this Constitution or the constitution of any state, nor state or federal law, shall be construed to require that marital status or the legal incidents thereof be conferred upon unmarried couples or groups."

While claiming support in Congress, Matt Daniels, executive director of the Alliance for Marriage, would not release the names of any members of Congress who support the amendment.

Daniels argued that the amendment would strengthen the sanctity of traditional marriage, and would preclude "the courts from distorting existing constitutional or statutory law" to require that "other pairings and groupings" get the same legal benefits as married couples.

Bob Laird, of the Office for Family Life in the Roman Catholic Diocese of Arlington, Va., and member of the Alliance's advisory board, charged that "the courts in America are poised to erase the legal road map to marriage and the family from American law within this decade."

But Christopher Anders, legislative counsel for the American Civil Liberties Union, said the proposed amendment would actively cut citizens off from benefits and protections and would be using the U.S. Constitution to wield a discriminatory sword against members of certain groups.

"The few amendments to the Constitution that have been adopted in the last two hundred years are the source of most of the Constitution's protections for individuals rights," Anders said. "The proposed amendment, by contrast, would deny all protection for the most personal decisions made by millions of families."

"This amendment is the legal equivalent of a nuclear bomb," Anders added. "It will wipe out every single law protecting gay and lesbian families and other unmarried couples. It's a problem for anyone who is in a relationship they're not married into."

Walter Fauntroy, a member of the Alliance's board of directors, who is also pastor of a Washington, D.C., church and a former District of Columbia delegate to the House of Representatives, insists the proposed amendment is not discriminatory and would not preclude state legislatures from recognizing civil unions.

"As a black man," Fauntroy stressed, "I am fierce about protecting the rights of everyone."  But he argued that same-sex unions "tamper" with the institution of marriage.

Some constitutional scholars have reservations about such an amendment.

"We don't like amending the Constitution often," said Douglas Kmiec, a law professor at Pepperdine University Law School in Malibu, Calif., "and especially for specific subjects. States are capable of resolving this themselves."

Kmiec says he personally believes marriage between a man and a woman is "sanctionally unique." But he adds, "I don't want this constitutional amendment used to hate or discriminate" against gays and lesbians.

"If it's constitutionally unnecessary, then you run the risk of being discriminatory," he said.

Thirty-four states have adopted "defense of marriage" laws that restrict the definition of marriage to a union between a man and a woman.

The federal Defense of Marriage Act, passed by Congress and signed by President Bill Clinton in 1996, assures that no state is obligated to recognize the legal status of civil unions or other same-sex partnerships granted in other states.

But dozens of cities have adopted civil-union laws extending protections and benefits to same-sex couples, and Vermont became the first state to pass such a law last year.

Since then, 2,300 same-sex couples, many of them out-of-state residents, have been bound in Vermont in formal ceremonies.

There are 27 amendments to the Constitution, with only one having been added in the past 30 years. Successful amendments must be ratified by two-thirds majority votes in both houses of Congress and simple majority votes in 38 state legislatures, three-quarters of the total.