Poland's Roman Catholic Church today sided with the independent trade union Solidarity in a strong warning to the Polish parliament not to pass emergency powers legislation sought by the government.

In a letter addressed to the assembly, Archbishop Jozef Glemp said adoption of the act, which the Communist authorities say is necessary to curb widespread work stoppages, would itself provoke greater conflict. Considering Poland's already dire social and economic situation, the primate said, further conflict should be avoided.

The letter, mailed yesterday and signed by Glemp in the name of all the Polish bishops, represents a forceful interjection into a major political dispute between Polish authorities and Solidarity by the church, which has generally done its mediating quietly.

Since being named head of the powerful Polish church in July, following the death of Cardinal Stefan Wyszynski, the 52-year-old archbishop personally has carried on the tradition established by his predecessor of dialogue and cooperation with Poland's opposing forces. Glemp at times appears even more active.

A spokesman said the Polish primate also sent letters yesterday to Solidarity chairman Lech Walesa and the Communist Party chief, Gen. Wojciech Jaruzelski, pressing them to bring their groups back into working contact after the eruption of new tensions in recent days.

The church's firm rejection of the emergency powers legislation, though, was a clear blow against the government, swinging the weight of the archbishop's moral authority to Solidarity's cause. The flurry of Glemp's letter-writing would appear to be a barometer of the considerable concern with which senior church officials view the renewed confrontation between Solidarity and the authorities.

Meanwhile, parliamentary deputies, who during the year have been trying to establish a larger, more defined role for themselves in Poland's changing power structure, seemed inclined to steer clear of the emergency powers issue for now. The agendas, announced today, for the coming two weeks' parliamentary sessions show a logjam of bills ranging from economic to educational reforms but no mention of measures to limit civil rights.

Defending the need for an emergency powers law, Warsaw officials have charged Solidarity members with abusing the right to strike granted Polish workers in August 1980. Officials say that measures that would allow them to suspend the right to strike and ban certain gatherings are necessary if Poland is to survive the winter and get back to work.

But Solidarity's leadership last week threatened a general strike if the government obtained and enforced such measures. The threat came at the top of a list of union complaints and allegations that marked a sharp threat to Poland's uneasy peace.

Glemp said in his letter that any attempt now to limit seriously the right to strike and other civil liberties "would threaten unrest considering the great pressures from the union's base on the union leadership and the demands for a general strike."

"At this moment, no widespread strike actions endanger the country's situation," the primate stated. "Passing an antistrike law now could lead to a wave of strikes with unknown and unforeseeable range and consequences."

In yet another letter, the archbishop today endorsed the back-to-class call issued yesterday by student strike groups that had been staging sit-ins at more than 80 Polish universities since early November.

Although students at about 30 schools today decided not to heed the appeal by the Independent Student Association and national strike committees to stop the protest, a number of other universities were reported returning to normal.

In relation to the major issues of economic and societal control over which the Warsaw authorities and Solidarity have been tangling, the student protest has served as a curious sideshow. The most substantial demand -- the introduction into parliament of a higher education bill providing for greater democratization of university life -- was met several weeks ago.

But the strike continued, largely in sympathy with students at one school, Radom Engineering, who were upset over one man, Michal Hebda, the rector. Hebda, who has a reputation as a taskmasker and believer in one-man rule, was reelected to his post earlier this autumn under less-than-democratic circumstances that created an uproar. He has yet to be removed.

"No one who is wise can question the accomplishments you have gained by your stand," Glemp wrote to the chairman of the Independent Student Association. "Your accomplishments seen in historical, social and moral perspective are huge. You have protested against breaking justice. You came out for freedom of education and scientific research. You have gained maturity by uniting with discipline in strike-time difficulties."