MEXICO CITY— Forbidden love can be the most passionate, and one story of forbidden love recently ignited the passions of this country's powerful Roman Catholic Church, turning a low-budget movie into the biggest box office hit in the history of Mexican film.

It is the story of Amaro and Amelia, young and raging with hormones. They steal their first kiss on the pews of a candlelit church. They whisper sweet nothings during confession. And Amaro takes Amelia's virginity under a sky-blue veil embroidered with stars, resembling the veil worn by the Virgin of Guadalupe, Mexico's patron saint.

That alone might have been enough to ignite religious outrage in a country more than 90 percent Roman Catholic. But there is more: Amaro is a priest. The Catholic hierarchy here, which has all but prohibited public discussion of real-life misdeeds by the church, responded by mounting nationwide protests to stop the movie.

''The Crime of Father Amaro,'' directed by Carlos Carrera and based on a 19th-century Portuguese novel, has played for about three months in Mexico and is scheduled for release in New York and elsewhere in the United States on Nov. 15.

It portrays priests as predators, drunk with power and lust. They murder; they take money and favors from drug traffickers; they take personal pleasures from lonely widows and innocent virgins.

Toward the end of the film, Amelia becomes pregnant by Father Amaro. Abortion is illegal in Mexico -- except in cases of rape or if the mother's life is in danger -- and considered immoral by the Catholic Church. But Father Amaro forces Amelia to have a clandestine abortion, an action that leads to the film's tragic conclusion.

In the weeks before the movie's Mexican premiere in August, priests and cardinals staged news conferences and demanded meetings with high-level government officials. They called the film a ''frontal attack'' on the Roman Catholic Church, sought to have it banned from Mexican theaters and warned the film's stars, Gael García Bernal and Ana Claudia Talancón, that they could be excommunicated.

Abortion opponents summoned armies of young people to pass out fliers at shopping malls and outside churches across the country, pleading with parishioners not to see a movie that they said mocked Mexico's patron saint.

''We call on those who believe, who love the Virgin and who love the Eucharist,'' said Jorge Serrano Limón, president of Pro-Life Mexico. ''It makes no sense to go see the film.''

The Mexican film industry, which still receives government financing for most of its productions, had endured tough censorship under the authoritarian Institutional Revolutionary Party, or PRI, which had governed Mexico for more than seven decades.

The PRI upheld strict laws separating the powers of church and state, including laws that prohibited the church from owning property and running schools. But it also turned a blind eye to many of the church's abuses and protected it from public scandal and most artistic criticism.

In recent years, church pressure kept Arturo Ripstein's ''Black Widow'' out of Mexican theaters for six years. The film portrays a priest who tells his mistress the secrets of his parishioners' confessions. Martin Scorsese's ''Last Temptation of Christ'' was never released in Mexican theaters.

The PRI was ousted two years ago, when voters elected the opposition leader Vicente Fox. Catholic officials believed that the political tide had shifted even more in their favor. President Fox, a leader of the conservative National Action Party, is the most openly Catholic president since the Mexican Revolution. His mother was quoted in the Mexican press as calling the film ''garbage,'' without having seen it.

But Mr. Fox said he would not allow personal morals to overrule freedom of expression, and his government refused to ban ''The Crime of Father Amaro.'' Officials reportedly asked the producers of the film, however, to delay its release until after a visit to Mexico by Pope John Paul II.

In the end, the scandal surrounding the film helped turn it into the blockbuster hit of the summer. The movie opened in about 360 theaters across the country, a record for Mexican films, and earned more than $3 million in its first weekend, more than the Mexican hit ''Y Tu Mama Tambien,'' which was also released in the United States. Newspaper polls taken soon after the movie opened showed that around 70 percent of those who had gone to see it did not consider it offensive to their religious beliefs.

Eduardo Álvaro, a movie critic, wrote that the film exposed the ''enormous gulf between the teachings of the church and the beliefs of Catholics.''

Bishop Felipe Arizmendi, from the southern state of Chiapas, said the campaign by the church had been ''counterproductive.''

''It served to generate more propaganda,'' he said. ''Now many people will go to see the movie out of morbidity or curiosity.''

One of the film's producers, Daniel Birman Ripstein of Alameda films, who is Arturo Ripstein's nephew, said he knew the movie broached an explosive topic. It took him more than seven years to get financing, and his grandfather, the producer Alfredo Ripstein Jr., had been trying to get support for the film since 1970.

To get permission from Catholic officials to film inside churches, members of the film crew resorted to some subterfuge, giving false titles for the movie. Mr. Birman Ripstein said he had not wanted the news media to publicize the project before it was completed.

Mr. Carrera, the director, said, ''I believe it is very important that the film exists, and that the public reacted the way it did.''

''It is very healthy that the church understands that it no longer has so much power, that its power is not absolute,'' he said. ''It must now be very clear to the church that at least in terms of censorship, it has no influence.''

Photos: A moviegoer in Mexico City viewing a poster for ''The Crime of Father Amaro.'' The movie has been denounced by the Roman Catholic Church and was the blockbuster hit of the summer in Mexico.; Carlos Carrera, the director of the movie, at his home in Mexico City. (Photographs by Lynsey Addario/Corbis Saba, for The New York Times)