* Online survey shows Colombians divided on issue

* Rejection comes shortly after France approves gay weddings

By Eduardo Garcia and Carlos Vargas

BOGOTA, April 24 (Reuters) - Colombian lawmakers on Wednesday rejected a polarizing bill to allow same-sex marriage in the predominantly Roman Catholic nation, as hundreds of people took to the streets to demonstrate for and against the measure.

The bill was rejected by 51 out of 102 lawmakers in the Senate - with 17 in favor. The negative vote was widely expected, given that lawmakers from the ruling coalition had made an alliance to oppose the initiative.

Several hundred people rallied in Bogota's main colonial square as lawmakers debated the proposal to allow people of the same sex to marry. Colombians for and against the bill faced off in the Plaza Bolivar, with some critics of same-sex marriage waving banners that read: "1 man + 1 woman = marriage."

Elsewhere in Latin America, gay marriage is allowed in Argentina and Uruguay as well as Mexico City and some parts of Brazil.

In an online survey being conducted by Colombian daily El Espectador, nearly 53 of readers have supported the bill, while some 46 percent are opposed. About 26,000 people have participated. No margin of error was given.

Colombian President Juan Manuel Santos has not taken a position on the measure.

Critics of the bill have voiced concerns that allowing gay couples to marry would be a blow to the "sanctity" of marriage.

"Marriage as an institution, as a sacrament, implies a union between a man and a woman with the idea of procreating," said Senator Carlos Ramiro Chavarro, a Conservative Party lawmaker.

"I respect homosexual relations ... but a minority should not impose legislation because the Colombian state must legislate for the majority, and the majority want us to preserve the nuclear family," he said.

Such comments angered Senator Armando Benedetti, who proposed the bill.

"They have always said that this project goes against nature, that it goes against the foundation of society and against God's law," Benedetti said on Monday.

"Those who vote against this project ... would have voted in favor of slavery."

The rejection came a day after France approved a reform to allow gay couples to marry, a pledge by President Francois Hollande that sparked violent street protests and a rise in homophobic attacks.

Last week, New Zealand became the first country in the Asia Pacific region to allow gay weddings in a vote that prompted cheers, applause and the singing of a traditional Maori celebratory song in parliament.

Countries where gay marriages are legal include Canada, Spain and Sweden. Washington, D.C., and nine states have legalized same-sex marriage in the United States.

(Writing by Eduardo Garcia; Editing by Peter Cooney)

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