Senator Cory Bernardi spearheaded the anti same sex marriage campaign's national launch in Sydney, joined by prominent coalition politicians Matt Canavan and Concetta Fierravanti-Wells, who all took to the podium under blue and pink lights to champion the no vote.
Meanwhile, outspoken advocates of the yes campaign are pushing supporters to get their vote in the post.
An estimated 1000 people, many with shirts and placards bearing the slogan 'It's ok to say 'no', filled the International Conference Centre at Darling Harbour on Saturday night.
The Coalition for Marriage, the group at the centre of the campaign headed by Australian Christian Lobby chief Lyle Shelton, placed the focus on the flow-on effects of altering marriage.
The auditorium was cast in the group's thematic blue and pink light while its advertisements for a no vote in the postal survey were screened between speakers.
Senator Bernardi, who received a standing ovation, warned the audience of 'weaponised' anti-discrimination laws and 'legal warfare' against supporters of traditional marriage if the Marriage Act is changed to include same-sex couples.
Free speech was under attack from those seeking to redefine marriage, and their mission would have predictable consequences, he added.
'We're under assault because we're on the right side of legal and moral history,' he said.
Across Australia, well-known marriage equality advocates, political leaders, couples and campaigners will share their plans to encourage others to tick YES and post their forms back to the Austalian Bureau of Statistics.
Former prime minister Tony Abbott's sister and City of Sydney councillor Christine Forster and her partner Virginia Edwards will appear in Leichhardt in Sydney on Sunday morning to promote the yes campaign.