Following a four-day fact-finding trip to Nicaragua, representatives of religious groups encompassing a wide range of U.S. Christians called on the Carter administration yesterday to take immediate steps to facilitate the resignation of President Anastasio Somoza.

As a result of investigations they said had shown that "renewed, even more bloody armed conflict is held to be ineviatable and imminent," the clerics recommended the immediate withdrawal of the U.S military mission to Nicaragua and public insistence that U.S. allies cease supplying arms to the Somoza government.

The fact-finding team included the Rev. Alan McCoy, president of the Major Superiors of Men representing 70 Catholic orders; Dwain Epps, of the National Council of Churches, representing 31 Protestant denominations, and Wallace T. Collett, board chairman of the American Friends Service Committee.

Noting that Somoza has "lost nearly all support among the people" except for "his family, the National Guard he commands and a small remnant" of his own political party, they said that opposition to him "unites practically all sectors of the population."

The ecumenical delegation described current U.S. sponsored mediation efforts as "not credible to the Nicarguan people" and called on the United States to "exert its considerable influence to cause the mediating team to attend immediately to the preeminent requirement that Somoza step down and the National Guard be restructured."

The group released the report following its delivery yesterday to the State Department. The findings and recommendations coincide closely with those previously released by other American groups and also with the demands of both Nicaragua's political opposition and the Sandinista guerrillas.

A guerrilla attack last August on Managua's National Palace sparked a three-week civil war that led to the current military cease-fire and mediation. Well informed sources both here and in Managua have described the mediation effort as rapidly deteriorating after Somoma's public rejection of opposition demands that he resign. Many expect a new guerrila attack within weeks.

The religious team, meeting with reporters, carefully avoided direct criticism of the mediation effort itself. In the report the "strongly support the principle of mediation."

"There is a widespread belief in Nicaragua," the report said, "that the U.S. role in the three-nation mediation effort is more in defense of its own perceived security interests than it is in defense of justice for the Nicaraguan people . . . They perceive (it) as designed to gain time in which to assemble a replacement government that will suit U.S. interests.

"They had understood that the mediation was to be a means to rid the country of Somoza and restructure the National Guard. They now see it as an attempt to divide and weaken Somaza's opposition."

The delegates said they did not meet with Somoza during their trip, but talked with a "very broad spectrum of people," including high-level church and opposition political leaders, representatives of the three Sandinista factions, U.S. diplomatic and mediation officials in Managua and "representatives of the business and commerce sectors."

While both Epps and Father McCoy acknowledged having a predispostion against the Somoza government that had been expressed by their orgainzations, Collet described himself as a "businessman from Cincinnati" who had little knowledge of the Nicaraguan situation before his trip there early this month.

"I'm not a theologian," Collett said. "I'm a businessman. I think I can tell when somebody is lying to me and the people we talked to weren't lying."

In a visit to war-damaged areas, he said, "we saw what Somoza and his soldiers were willing to do to their own people, and you form your own conclusions."

Describing their recommendations as "not requiring any significant change" in U.S. policy, and in conformity with stated Carter adminitration goal, they called on the U.S. government to overcome what McCoy called its "crippling fear" of a communist takeover in Nicaragua, and its reluctance to recognize a legitimate opposition.

"There is a need for speed," McCoy said, U.S. "delaying tactics have cost many deaths."

The opposition people with which the team spoke, Epps said, "were not talking about revolution. They are capable, well-trained, responsible and representative people capable of stepping into positions of power tomorrow and taking steps toward elections and the establishment of a representative government."