The Polish government announced the initiation of clemency proceedings for political prisoners today but placed conditions on the measure that are expected to leave leading figures of the banned Solidarity trade union in jail.

A dispatch by the official PAP news agency released tonight said that prosecutors have been ordered by the government's prosecutor general to "review all proceedings against offenders" and "individually weigh the possibility of easing the legal sanctions against these offenders."

The PAP dispatch said prosecutors would decide on a case-by-case basis whether to free some of the 368 officially acknowledged political prisoners or ask courts for their release. However, it said the clemency proceedings "are not expected to cover" persons who have been imprisoned before, committed "particularly dangerous" offenses, or were covered by amnesties in 1983 and 1984.

The measure, which was officially labeled a "humanitarian initiative," fell far short of last year's sweeping amnesty and appeared to exclude more than half a dozen top Solidarity leaders who have been rearrested since then. Among them are Adam Michnik, Wladyslaw Frasyniuk and Bogdan Lis, who were sentenced to prison terms ranging from 2 1/2 to 3 1/2 years in June on charges of attempting to organize an illegal strike.

The limited release comes as a disappointment to opposition leaders as well as to the Roman Catholic Church, which called today for a full-scale amnesty and an expansion of political liberties. Diplomats said the government decision is also unlikely to result in a warming of relations with western governments, although that has been seen as one of the principal purposes of the initiative.

The Reagan administration has sharply criticized the trial and imprisonment of Michnik, Lis and Frasyniuk and the rearrest of other Solidarity activists. Diplomats here said that an amnesty excluding well-known prisoners probably would not result in any counterstep by Washington, such as the lifting of economic sanctions.

Polish leader Wojciech Jaruzelski first mentioned the possibility of an amnesty last month during a visit to the United States, saying that it would depend on the voter turnout for parliamentary elections Oct. 13. The government declared the elections a success, and official statements initially indicated that an amnesty would be considered by the new Sejm, or legislature, which is required by Polish law to approve such measures.

Two weeks ago, however, the government appeared to turn away from a broad release as the Communist-backed Patriotic Movement for National Birth issued a call for a more limited clemency act. Diplomats here said some officials in the government and Communist Party had objected to a general amnesty on the ground that it would result in a release of common criminals along with political prisoners and would mock Jaruzelski's warning last year that rearrested activists would be dealt with severely.

The PAP bulletin tonight said that the clemency had been approved Tuesday by the Communist Party Central Committee, which "confirmed the party's permanent readiness for dialogue and agreement with all who value the supreme weal of socialist Poland above resentments and differences of outlook."

PAP added, "The implementation of this humanitarian initiative gives those set free a chance to return to the path of respecting the law. It is also an expression of the state's magnanimity and hope that these people will observe the legal order in the future."

The report did not say how many prisoners might be released or how soon they might be freed. The procedure of case-by-case review by prosecutors suggested a gradual exodus of prisoners from jails in various parts of the country rather than a single, dramatic release.

PAP said that the measure would apply to persons under arrest but not yet sentenced as well as to "ongoing investigations." However, it was not clear tonight whether those terms would apply to Solidarity leader Lech Walesa, who is currently under investigation on charges of slander and instigating a strike.

[Walesa filed a protest today accusing a Gdansk prosecutor of acting illegally in the investigation, news services reported. Walesa said that police, who he said burst into his apartment Wednesday to take him to court for questioning, had upset his wife, Danuta, who is eight months pregnant with their eighth child. Walesa said that such police harassment was damaging his health.]

Two prominent underground Solidarity activists captured earlier this year, Czeslaw Bielecki and Tadeusz Jedynak, apparently would be excluded by the clemency provisions. Both men face major charges and could receive long jail terms if convicted.

The announcement of the clemency came just hours after Poland's Catholic bishops issued a statement calling for an amnesty and "the creation of possibilities and forms of social activities that would allow the constructive engagement of all citizens."

The statement, which followed a two-day bishops' conference, also expressed concern about the large number of prisoners in Polish jails and their treatment. Solidarity spokesmen and human rights groups recently have accused the authorities of beatings and other mistreatment of political prisoners.

Opposition sources said yesterday that Frasyniuk, who was reported to have been beaten in prison last month, was transferred Monday from Leczynca Prison in central Poland to a prison in the eastern part of the country without explanation. Other political prisoners at Leczynca, they said, were continuing a hunger strike to protest mistreatment and poor conditions.