Opponents of a gay marriage bill in Mexico City approved Monday by legislators say giving gay couples the right to adopt is going too far, the Informador reported.

The gay marriage bill – approved on a 39 to 20 vote that included five abstentions – is expected to be signed by Mayor Marcelo Ebrard of the progressive Democratic Revolution Party (Partido de la Revolution Democratica, PRD). The bill only effects Mexico City, one of the world's largest cities with nearly 9 million residents.

Members of the conservative National Action Party (Partido Accion Nacional, PAN) have vowed to appeal to the country's Supreme Court and urged Ebrard to veto the legislation.

Mariana Gozmez del Campo, who heads the PAN in Mexico City, said members of the PRD violated the rights of minors by allowing gay couples to adopt.

The Roman Catholic Church also took a hard line position, calling the bill an “immoral law.”

The Archbishop of Mexico, Cardinal Norberto Rivera Carrera, said gay adoption was “unacceptable and reprehensible” because such an upbringing would subject children to “such injustice.”

“Our children and youth are at grave risk, seeing as normal such unions, and may mistakenly understand that sex differences are simply a personality type, therefore failing to appreciate the duality of human sexuality, which is a condition of procreation and therefore, conservation and development of mankind,” he told the paper.

Latin America's first gay wedding was about to make history on December 1 in Buenos Aires, Argentina after a judge's ruling paved the way for two men to marry, but a national judge ordered a halt to the ceremony at the last moment. Argentina's top court has agreed to hear the case.

Mexico City is among a handful of cities in Latin American that recognize gay couples with civil unions, but only Uruguay has legalized such unions.

If approved, gay wedding bells might ring in the city as early February.