An advert urging Australians to vote against legalising same-sex marriage has been criticised for linking the debate to school gender education.
Australia will hold a non-binding postal survey next month to gauge support for changing its Marriage Act to include same-sex couples.
The No campaign has released its first advert, generating intense discussion.
Critics say it unfairly links the debate to school education programmes, but prominent figures have defended it.
The 30-second advert, by lobby group Coalition for Marriage, features three women expressing concerns about sex education in classrooms.
One woman says: "The school told my son he could wear a dress next year if he felt like it." Another says: "When same-sex marriage passes as law overseas, this type of programme becomes widespread and compulsory."
The advert concludes with a message: "In countries with gay marriage, parents have lost their right to choose." It does not provide evidence for its claims.
Same-sex marriage advocates have criticised the advert as misleading and irrelevant.
"They are putting up red herrings. They know a majority of Australians back equality, back a fair go for everybody, so they are trying to distract the nation with dishonest claims," a spokesman for lobby group The Equality Campaign told the BBC.
Leader of the Opposition Bill Shorten said the advert was "offensive and hurtful" to LGBT Australians and their families.
"This is not freedom of speech. This is freedom to hurt," he said.
Education Minister Simon Birmingham said the debate was simple and should not be conflated.
"It is patently ridiculous to suggest that allowing same-sex couples to marry is somehow going to see some new wave of teaching reform sweep across the country," he said.
Plea for respect
However, another government minister and same-sex marriage supporter, Josh Frydenberg, said he did not "have a problem" with the advert.
"I would just ask that all parties to this debate, both the for and the against case, ensure that they are respectful," he told the Australian Broadcasting Corp.
Senator Zed Seselja, a same-sex marriage opponent, said the advert represented freedom of speech.
"These mothers are clearly putting the case that their ability to object to fairly radical sex education in schools and the like will be much harder if you redefine marriage in the Marriage Act," he said.
The advert has earned both criticism and praise on social media.
Unless there is a successful court challenge, the postal survey will take place between 12 September and 27 October. The results are due to be announced on 15 November.
If the vote shows support for legalising same-sex marriage, a bill to change the law would be introduced to parliament.
However, MPs would not have to vote in line with the public.
The survey has faced criticism over fears it will unleash hatred, its cost of A$122m (£75m; $97m), and concerns that the postal method will alienate younger voters.
Recent polls, including one this month, have indicated a majority of Australians support changing the law.