Slovenian lawmakers have set a referendum on same-sex marriage for Dec. 20 after the bid was pushed through by conservative groups backed by the Catholic Church.

The group called "Children Are At Stake" has gathered 40,000 signatures needed to call a popular vote. The group has sought to challenge a law passed earlier this year that defines marriage as a union between two consenting adults.

Conservatives have argued the law paves the way for gay couples to also adopt children. Supporters of the law have insisted that human rights issues shouldn't be decided in a referendum, but the Constitutional Court has ruled the vote should be held after all.

Lawmakers determined the date for the referendum in a 69-11 vote on Wednesday.