Pope John Paul II, using the strongest language since he arrived in Brazil last week, told its bishops today that they are "prohibited" from engaging in partisan political activity and that the church must "recognize constituted authority" while carrying out its role of seeking social change.

The pope's speech to the national eucharistic conference was considered by observers here to be the most important of his trip, an attempt to clarify the line between what John Paul considers proper church activity on behalf of the poor and oppressed and what he sees as improper instrusion by the church in temporal political affairs. He seemed to rein in the more activist Brazilian bishops.

It was understood that the speech, drafted before the pope left Rome June 30, was "softened" here to reflect John Paul's first-hand impressions and growing sympathy for the work of the Brazilian church, one of the most liberal in Latin America.

Nonetheless, before specifically defending the church's "right and duty" to fight against social injustice, the pope warned the assembled bishops, nearly 300 of the 334 in Brazil, that "your vocation prohibits you, directly and in total clarity, from taking part in anything that appears to be politically partisan, subject to whatever ideology or system."

But, John continued, "You are not prohibited, indeed you are invited to be close to and in the service of all men, especially the most disabled and in need.

"The church reinvokes as its right and duty the practice of a social pastoral [program], not along purely temporal lines, but more as a formation and orientation of consciences, using its own specific terms, toward seeking a more just society."

The pope also urged the Brazilian church to remain united even if that means recognizing the differing points of view within in it. Although most of the bishops and priests are considered to be "progressives," that is, in agreement with the church's active role in supporting social causes on behalf of the poor, a significant minority is "moderate" or conservative," believing that the church should concentrate its resources on its traditional religious functions.

A working document presented by the bishops' council to the eucharistic conference here showed how close to the temporal world the Roman Catholic prelates have come, accusing the government of abetting racial discrimination -- "the Negro is despised" -- and failing to serve the poor.

The conference was called to deal with the problems of mirgation within Brazil as the poor leave their homes in search of jobs. Among the targets of bishops' document was "organized prostitution . . . the only consciously organized service offered to migrants."

Among the signers of the working document was Fortaleza's archbishop, Cardinal Aloisio Lorcheider. He had been an outspoken critic of the military government, joining other church activists in such untraditional stands as support of a recent metal-workers' strike in Sao Paulo. The government took the employers' side and eventually forced the workers to compromise on their wage demands.

During his trip, John Paul has spoken eloquently about the problems of the poor -- visiting a slum in Rio de Janeiro and meeting with workers in Sao Paulo -- and has warned business and military leaders that they face violence and revolution if they do not encourage broader distribution of wealth.

All of the problems that afflict Latin America are evident in Brazil, which over the past 15 years has experienced rapid economic growth under a military government yet has seen most of the benefits of its burgeoning economy accrue to the top 5 or 10 percent of its 120 million people.

More than half of Brazil's population remains illiterate, an estimated 30 million live in "absolute poverty," millions more suffer diseases attributable to their poor living conditions -- especially here in the northeast region.

In his address today, John Paul said he supports the need for special emphasis on social, economic and religious programs for the disadvantaged but he again cautioned the bishops that their church must reach out to all.

The pope also said that, in seeking better distribution of income and greater benefits for the poor, the church must not become involved in advocating social justice, a clear slap at some of Latin America's more radical priests.

While he was addressing the bishops, John Paul sent the Vatican's secretary of state, Cardinal Agostino Casaroli, to visit the families of three women trampled to death yesterday as a crowd surged forward to try to enter a soccer stadium where the pope was to appear. A spokesman said the pope asked Cardinal Casaroli to express his personal condolences and give his personal blessing to the women's families.