A bill aimed at banning gay marriage in Wyoming has been defeated in the House.

House Joint Resolution 17, also known as the “Defense of Marriage” resolution, died after an hour of debate Friday by a vote of 35-25.

Republican Representative Owen Petersen of Mountain View had sponsored the bill. The bill would have put the definition of marriage as a heterosexual union to a popular vote. If approved, the bill would have banned gay marriage by amending the Wyoming constitution.

The state of Wyoming currently bans gay marriage by law, but opponents say the state remains vulnerable without a constitutional amendment.

Thirty states have amended their constitutions to ban gay marriage. Some simply define marriage as a union between a man and a woman, while others go farther, explicitly denying any marriage-like recognition, including civil unions.

Focus on the Family Action, the Colorado Springs-based conservative Christian group, had been criticized for pushing to get the constitutional amendment on the ballot. In the weeks leading up to the vote, the group began a telephone lobbying campaign which encouraged voters to call lawmakers to support the anti-gay bill.

The newly formed WyWatch Family institute also supported the bill. The group is closely associated with Focus on the Family and the Arizona-based conservative Christian legal group the Alliance Defense Fund.

“We're trying to protect the children, because when you have a same-sex marriage, you're denying that child either a mother or a father,” WyWatch Chairwoman Becky Vandeberghe told the Associated Press prior to the vote. “And the family unit is very, very precious to us, and we want to make sure that every child has that.”

Vandeberghe called the defeat a “grave injustice.”

Gay groups hailed the vote. “We are grateful that the Wyoming House of Representatives stood up for equality and refused to write discrimination in the state Constitution,” said Joe Solmonese, president of Human Rights Campaign, the nation's largest gay and lesbian rights advocacy group.

Legislators in Indiana have proposed a similar measure. But the bill would need to pass through two legislative sessions before arriving at the ballot box in November of 2012.