Pope John Paul II delivered a strong appeal to the Haitian Catholic Church today to carry the banner of human rights and social justice in this Caribbean island nation notorious for its poverty and political repression.

"Christians have noticed the division, the injustice, the excessive inequality, the degradation of the quality of life, the misery, the hunger, the fear of many people," the pontiff said in an open-air mass with President Jean-Claude Duvalier looking on.

"They have thought about peasants unable to live from their land, people who pile up without work in the cities, dislocated families, victims of various frustrations," the pope said. "However, they are convinced that there are solutions. The poor of all sorts must hope again."

With his direct language, John Paul plunged into the burning issue of Haiti as he has in various countries throughout the eight-nation Central American and Caribbean tour, of which today's 10-hour stop marked the final chapter.

Here, perhaps more than elsewhere, however, he seemed to encourage the Roman Catholic Church that he heads toward an active role in fighting political abuses and social inequalities connected with Haiti's 25-year Duvalier family rule.

Before the pope spoke, Duvalier, in his welcoming speech, announced that he was "waiving" his future rights, under an 1860 concordat between Haiti and the Vatican, to designate the country's bishops.

Referring to Pope Paul VI's decision in 1966 to transfer control of the Haitian church from foreign missionaries to an indigenous hierarchy, Duvalier told John Paul:

"At this time in the same spirit in order to complete the symbiosis between church and state and follow the teachings of Vatican II, I intend from now on to waive my concordatory rights and privileges to allow the Vatican to appoint archbishops and bishops. This new step, which will permit the strengthening of the church's economy, will be effective while obviously taking into account the legitimate concerns of a sovereign state."

John Paul, who began the day with a visit to Belize, a former British colony in Central America, was returning to Rome tonight.

Referring in his speech here to Haiti's social inequities, the pontiff declared that "the church retains in this field a prophetic mission inseparable from its religious mission. And it demands the freedom to carry it out; not to accuse, and not only to bring out an awareness of evil, but to contribute in a positive way to improvement, to enlist consciences, particularly the consciences of those who carry responsibility in villages, cities and at the national level, to act according to the gospel and social doctrine of the church."

The pontiff referred to a symposium last December in which the bishops of Haiti denounced the country's social and political ills in unusually strong language and pledged to work toward improvements. The symposium statement came against a background of reports leaked by the Haitian clergy that Foreign Minister Jean-Robert Estime had warned the country's seven bishops to avoid public stands that could be interpreted against the government.

"I have read the message from last December's symposium," John Paul said. "I have come here to encourage my brothers and sisters in Haiti to carry it out. . . . I have come to encourage this awakening, this leap, this movement of the church for the good of the whole country."

The latest and so far most-noticed stand taken by the Haitian church came in an open letter Jan. 27 demanding, in the name of the pope's impending visit, that an imprisoned activist cleric be released. About two weeks later--three weeks before today's visit--the priest was released.

Friends said the Haitian cleric, Gerard Duclerville, reported he was severely and repeatedly beaten during his 42 days behind bars. Although the pope made no public mention of his case today, the bishops' appeal was considered here to be a watershed in official church action defending political rights. "Today it is Gerard and all those whose name we do not know," said the bishops' letter, ordered read at all masses. "Tomorrow it will be you, we, I, or somebody else. Where a man is humiliated and tortured, it is the whole of humanity that is humiliated and tortured."

Archbishop Wolf Ligonde, head of the Haitian church, joined in signing the letter. The archbishop, a cousin of Duvalier's wife, Michelle, previously had been regarded by some Haitian clergymen as unacceptably reticent on taking a strong position against governmental abuses here.

Foreign observers, including priests, report that political repression has eased since Jean Claude Duvalier took over from his father at age 19 in 1971. His government recently announced formation of a human rights committee, for example, and the U.S. State Department's annual human rights report noted progress in the field.

Many of the dictatorial practices set up over the years by his father, Francois Duvalier, remain in place, however, and a number of dissidents have been arrested or forced into exile.

A per capita income of less than $300 a year makes Haiti the poorest country in the Americas. Against this background, John Paul issued his appeal for change based on Christian doctrine.

"There is indeed a deep need for justice, better distribution of wealth, more equitable organization of society, more participation, a more disinterested concept of service by all those who have responsibilities," he said.

"There is the legitimate desire by the media and politics for free, respectful expression of the opinions of others and of the common good. There is the need of more open and easier access to wealth and services that cannot remain the privilege of a few."

A smattering of applause arose from the thousands of Haitians gathered in sticky tropical heat as John Paul read his sermon in French during mass at Francois Duvalier International Airport. The 62-year-old pontiff, although draped in layers of white vestments, distributed communion to scores of Haitians in the late afternoon sun without visibly wilting.

Despite his appeal to the Haitian church, the pope reiterated warnings against clerical involvement in ideology or politics during a later address opening the General Assembly of the Latin American bishops' conference, known by its Spanish-language acronym as CELAM. While urging the more than 60 Latin American bishops meeting here to uphold the church's social teachings, he underlined principles set forth at an earlier conference in Puebla, Mexico, in January 1979 ordering clergymen to emphasize their evangelical role.

At the same time, he indirectly warned against inroads against the Catholic Church in recent years by fundamentalist Protestant sects spreading in Latin America. These movements, which he said sometimes "lack the true apostolic message," can create obstacles for the Catholic Church and other traditional Protestant churches, he said.

In his sermon at mass, John Paul also cautioned Haitians against the voodoo practices often mixed with Catholicism among the country's Roman Catholic majority. Without directly mentioning voodoo, he urged that Haitians make sure their religious devotion "not be a new form of submission to the elements of the world, a new slavery, as in certain syncretic practices, inspired by fear and anguish in the face of forces that one does not understand."