The Chilean Catholic Church has added 20 more names to its list of missing persons it charges were "detained or kidnaped" and stepped up its efforts to obtain a special Supreme Court investigation of the fate of the victims.

Episcopal vicar Christian Precht, head of the church's Vicarate of Solidarily, said in a brief filed Monday that the 20 persons disappeared in the last four months of 1976 and that "more and more frequently" mutilated bodies of unidentifiable persons have been found.

The 20 bring to 435 the list of missing persons for which the church says it has unassailable evidence of arrest or kidnaping by government security police.

The list was presented to the Supreme Court Dec. 24 - the tenth such attempt by the church to have the court appoint a special investigating judge - and is made up of the cases with the strongest evidence from among the approximately 1000 persons who, according to their families, disappeared after their arrest by security police in the past three years. Monday's brief was to provide additional arguments to the latest petition, expected to be decided by the court before the end of this month.

The court rejected all the earlier requests, which began in early 1975 with a list of 163 persons, on the grounds that individual investigations carried out by judges on a case by case basis were sufficient. Precht said in the petition Monday that such routine judicial probes had acquired an image of "ineffectuality" because none of them had turned up evidence of the guilty parties, even though the fact of "kidnaping or illegal arrest had been established."

In one of its rejections, in October, the Supreme Court attempted to discredit the church's list by saying 11 of the allegedly missing persons were actually imprisoned under state-of-seige laws. When the government in November released all state-of-seige prisoners except one, the church returned to the court claiming that none of the missing persons on its list were among the 320 released, and that the 11 names provided by the court in October did not match any of the names of those the church claimed to be missing.

Precht charged in the brief that "the disappearance or kidnaping of persons has become a tragically habitual occurence in our country in recent years."

"Likewise," he added, "the discovery of mutilated and unidentifiable bodies has become more and more frequent." He said the discoveries stirred "justifiable alarm" among the relatives of missing persons.

According to other church sources, some 30 unrecognizable bodies have been found in rivers and irrigation canals since May, many of them with fingers cut off and arms tied with wire. One of the bodies found on a beach last September was identified by a dentist as that of Marta Ugarte, 42, a leftist and a minor official in the previous government overthrown by the military junta. Ugarte's relatives had sought a habeas corpus writ from a Chilean court when she disappeared in August, charging that she had been arrested.