Gustavo Hasbun, an UDI member of Chile's House of Representatives who last week along with colleague Gonzalo Arenas introduced a bill to amend Chile's Constitution to ban gay marriage, says he acted because he fears a proposed civil unions bill could lead to full marriage for gay and lesbian couples in Chile.

Last week, President Sebastian Pinera sent to Congress a bill that would grant gay and lesbian couples many of the rights and benefits of marriage. The Life Partner Agreement (Acuerdo de Vida en Pareja or AVP) would allow gay and straight couples who have lived together for more than one year to enter the union.

The president signed his bill to the cheers of gay rights activists, but angry leaders of his center-right coalition, which includes the Independent Democrat Union (Union Democrata Independiente or UDI) Party, refused to attend the signing ceremony.

Two days later, on Thursday, Hasbun and Arenas introduced their measure.

In an interview with ADN Radio Chile, Hasbun said he supported Pinera's AVP bill, but then added that the amendment was needed because civil unions approach marriage.

“It is not necessary to create this parallel institution because this will weaken, in one way or another, marriage,” Hasbun said.

“I think a civil registration is no different today than a marriage in disguise. And that creates a lot of concern. And basically that's why I introduced the constitutional reform to ensure that marriage remains between heterosexual couples. But that doesn't mean we oppose the” proposed civil unions law, “because they effectively approach a gay marriage.”