Twenty-three Roman Catholic bishops said here yesterday they are "gravely concerned" that preoccupation with abortion is overshadowing "the threat of nuclear warfare" in voters' evaluations of candidates for public office during the current campaign.

"One cannot examine abortion as though that were the only moral issue facing our people," the bishops said in a statement released at a Georgetown University press conference.

The statement, issued two weeks before an election in which religious issues have become controversial campaign issues, supports the official position of the Catholic hierarchy in the U.S.

Two weeks ago, Bishop James W. Malone of Youngstown, president of the National Conference of Catholic Bishops, reminded Catholic voters that the church is not a "one-issue church" but has a "total life ethic." His statement came in the wake of controversies over the suggestion by some prominent bishops that the abortion issue should be the litmus test for selecting public officials.

The statement yesterday emphasized that the official position of the U.S. Catholic hierarchy holds that "not only abortion . . . but a spectrum of moral concerns that support the life and dignity of human beings at every level" is at issue in the forthcoming election.

Auxiliary Bishop Thomas J. Gumbleton of Detroit said the statement grew out of concerns expressed earlier this month at a meeting of Pax Christi USA, a Catholic peace group, that abortion has virtually eclipsed campaign debate on the nuclear threat. The statement is an effort to call the church back to consideration of nuclear war "as a deeply religious question, one that threatens the creation itself," the bishops said.

Gumbleton, the leading "dove" on the committee, which two years ago drafted the bishops' pastoral letter condemning most uses of nuclear weapons, said the 23 bishops signing the statement "all share the abhorrence of abortion . . .

"We are together on the moral issue but not on the political application," he said. "The position of our statement is the position of the National Conference of Catholic Bishops as a whole."

Last spring, Malone, as president of the bishops' conference, issued a statement urging Catholics to consider a range of issues in evaluating candidates for public office and to avoid single-issue politics.

As the political race heated up in late summer, however, a number of prelates in highly visible posts including New York, Boston and Philadelphia issued pronouncements that seemed to make abortion the preeminent issue.

"If I were a Catholic voter reading these statements, I would be confused . . . I would begin to think that you have to vote on the basis of that abortion issue," Gumbleton said.

Both Gumbleton and retired Bishop Carroll T. Dozier of Memphis emphasized that yesterday's statement supports the official position of the hierarchy.

Yesterday's statement by the bishops praised Cardinal Joseph L. Bernardin of Chicago for his now-famous "seamless garment" metaphor linking abortion, nuclear war and other human life issues into "a unified vision of life." Bernardin is expected to elaborate on his views in an appearance at Georgetown University on Thursday evening.

The bishops attacked as unrealistic the claim by some that nuclear war "is only a potential evil and that abortion is actual . . . There can be no possibility of exercising moral responsibility against nuclear war if we wait until the missiles have been released."

Gumbleton said there was no effort to poll the nearly 300 U.S. bishops in soliciting signatures to the statement released yesterday. Rather, he explained, the statement was sent on Oct. 8 to "about 50 bishops" who are members of Pax Christi, and with "no phone calls, no follow-up" the 23 had responded by Oct. 17. "We felt that was enough."

Bishops from this area signing the statement include Bishop Walter F. Sullivan of Richmond and Auxiliary Bishop P. Francis Murphy of Baltimore.