The Roman Catholic bishops' proposed pastoral letter on nuclear war, which they debated at their annual meeting here last week, continues to draw responses both here and abroad.

A multidisciplinary group of 21 present and former government officials, church leaders and atomic scientists has issued an open letter defending both the process and the general conclusions of the bishops' lengthy position paper.

And in a highly unusual step, an official of the West German government attacked the American bishops' position that first-strike use of nuclear weapons was immoral. Alois Mertes of the Ministry of Foreign Affairs, who said he was speaking for West German Chancellor Helmut Kohl, charged that the American bishops' statement, if adopted at a special meeting in May, would "weaken the credibility of the American deterrent" in Western Europe defense strategy.

The West German Catholic bishops have not taken a position on nuclear weapons, but the American hierarchy has been in communication with them on the progress of the pastoral being developed by the United States prelates.

The letter from scientists and others, whose signers ranged from former CIA director William E. Colby to former Atomic Energy Commission chairman Glenn T. Seaborg, expressed "full support for the bishops' right, in fact their obligation, to speak out on what is unquestionably the most urgent and difficult moral problem that humankind has ever faced."

Their letter was an attempt, the signers said, to counter critics who claimed the bishops should not meddle in international affairs because they lack expertise.

In preparation for drafting their pastoral, the scientists and academics said, the bishops "took counsel with a substantial number of well-informed civilian and military leaders, and we suspect that as a result they are better informed technically than most of their critics."

Recalling charges by the Nazis in World War II that Jews were a threat to the German nation, the letter asks, "Would it have been meddling in secular affairs had the bishops of Germany and of the world addressed themselves directly to that abomination?"

Signers of the letter include physicist Hans Bethe of Cornell University, Sen. Mark O. Hatfield (R-Ore.); Philip M. Klutznick, former secretary of commerce; Gerard C. Smith and Paul Warnke, chief U.S. negotiators for Salt I and II, respectively; and Jerome Wiesner, former president of the Massachusetts Institute of Technology and science adviser to President Kennedy.

In a related development, Bishop Joseph Hart of Cheyenne, has sent a letter to Catholics in his diocese "to say 'no'" to President Reagan's proposal earlier this week for basing of 100 MX missiles in a closely spaced "Dense Pack" formation near Cheyenne.

In a letter written in anticipation of Reagan's decision to base the MX in Wyoming, Hart wrote that the MX system "has destructive proportions far beyond anything now present in our land.

"If, indeed, as we are told, the MX missile system offers a 'first strike' capability, then it is morally indefensible," Hart wrote. "If that is the case, we no longer concern ourselves with deterrence but with aggression."

"We must call upon our congressional and state leaders, our government and our president to halt the arms escalation now, and to begin with the MX missile," Hart wrote Wyoming Catholics.

Claire Randall, head of the National Council of Churches -- a body not unfamiliar with criticism -- issued a personal statement deploring "the pressure and even hostility that has greeted" the bishops nuclear warfare pastoral.

"The bishops have every right to bring their understanding of the will of our Lord and Savior to the use of nuclear weapons," she said. "This is a question of human life, its significance and its survival. These are moral issues."

Among those criticizing the bishops last week was a new lay-edited publication called "Catholicism in Crisis," launched in the shadow of the bishops' gathering here last week.

The modest 16-page monthly is needed, its founders declared in a press announcement, because of growing "clerical domination" in the church affairs; because "the diversity of opinion among intelligent Catholics is overridden by precipitous press releases in the name of the bishops," and to counter "the leftward drift of the bishops' advisers" who tug the bishops "in the direction of foreign policy when the domestic situation in the American church calls out for their moral and spiritual leadership."

The most extensive article in the first issue, by executive editor Michael Novak, challenges the bishops' criticism of nuclear deterrence and their admonition to lay Catholics involved in nuclear defense efforts at any level to evaluate their jobs in the light of church standards of morality.

"Such teaching by the Catholic bishops will make all Catholic political leaders and military men suspect, as being, in effect, unreliable in time of crisis. The Catholic church will be acting as a sect," Novak warned.

The bishops, Novak charged, "are unwittingly leading the U.S. down the road, not of peace, but of appeasement and surrender."