Poland's bishops today addressed special messages to the martial law authorities and to believers in this overwhelmingly Roman Catholic nation outlining church policy following the military crackdown.

The contents of the messages, drawn up at a special conference in Warsaw of the country's 78 bishops, were not immediately known. But Western diplomats here speculated that they were likely to combine an appeal to society for calm with a strong condemnation of the government for its continued repressive policies.

The church has emerged as a key intermediary between the government of Gen. Wojciech Jaruzelski and the independent Solidarity trade union federation since the imposition of martial law Dec. 13. Catholic leaders, including the primate of Poland, Archbishop Jozef Glemp, have been involved in private negotiations to seek the release of Solidarity leader Lech Walesa and thousands of other detainees.

The bishops' conference, which took place yesterday, was the first meeting of the full Polish episcopate since the military takeover. The bishops had been unable to gather earlier because of restrictions on travel.

A communique published today said that the main subject at the meeting concerned "the pastoral tasks of the church in the current, very complicated, situation of the country."

The message to the faithful is scheduled to be read aloud in all Polish churches later this month. The bishops also decided to declare Feb. 2 "a day of prayer" for all those helping Poland.

In earlier sermons and letters to Jaruzelski, Glemp has called for the release of detainees and the ending of the practice of demanding loyalty oaths from Solidarity activists.

The recently appointed head of the Communist Party's Institute for the Study of Marxism-Leninism called for a political solution to the crisis. Jerzy Wiatr, a prominent sociologist identified with reformers in the party, said there was a need to restore the political system's ability to function "without the protective shield of martial law."

Wiatr said political reforms, such as the introduction of self-management in industry, had to be implemented in addition to economic measures.

"This is the only way for Poland if the last two decades of the 20th century are to go down in history as a period of progress rather than disintegration and decline," Wiatr wrote.

The problem facing reform-minded Communists like Wiatr is that martial law has a logic of its own. Thus, while he calls for the "creation of a climate favoring the development of science and culture," many fellow university professors are complaining of a general stultification of the country's intellectual life since the military takeover.

Meanwhile workers in some factories were reported to be continuing a campaign of passive resistance. A clandestine Solidarity bulletin, The News, said that in the three weeks after martial law only 1,065 cars out of 7,000 planned vehicles were produced at Warsaw's FSO car factory.