High-profile Coalition MPs past and present are set to launch a campaign on Monday to persuade Australians to vote "yes" in the same-sex marriage postal survey.
Former NSW premier Nick Greiner, Melbourne lord mayor Robert Doyle and Howard government cabinet minister Amanda Vanstone will lead the "Libs and Nats for Yes" campaign, while cabinet ministers including Kelly O'Dwyer and Simon Birmingham are also set to play a big role in the campaign.
While all but a handful of Labor MPs and all of the Greens MPs back same-sex marriage, the Coalition is split between supporters and opponents of a law change; to date, the "no" campaigners in the Coalition have dominated debate within the party and in the public sphere.
The new campaign group is led by Andrew Bragg, who was until recently the acting federal director of the Liberal Party, and hopes to persuade voters of the case for same-sex marriage within the liberal and conservative traditions embodied by the Liberal Party.
The campaign has released a short ad in which a series of voters declare it is time to vote "yes" for same-sex marriage, while also declaring their allegiance as Coalition voters.
Mr Greiner said he had joined the "yes" campaign because one of his children, Justin, could get married and the other, Kara, could not – and that struck him as fundamentally unfair.
"I have two kids, one of whom is in a model of a traditional marriage, one of of whom is in a model of a same-sex relationship. I don't see how in heaven's name we can ask their kids [Mr Greiner's grandchildren] to think it's acceptable that one partnership is inferior to the other," he said.
" I don't see why my grandchildren should be subject to a different state or government view of their parents' relationship.
"This is a classic conservative issue, both in the sense of being pro-marriage, and a Liberal issue in terms of being about freedom of choice."
Melbourne lord mayor Cr Doyle, who was one of the first elected Coalition officials in the country to back same-sex marriage, said his wife had had a profound effect on his thinking about the issue in recent years – in particular, that the law change would not just happen, but that it had to be fought for.
"I look at this city, we speak 240 languages, we come from 200 countries and we are still one city. We have a history of being one Melbourne – tolerant, diverse, creative and with different cultures and nationalities and interests," he said.
"So if that's all true, there is just one part where we are not equal – some of our colleagues, friends and family can't get married to the person they love."
He also made an appeal for respectful debate.
"I know people will disagree with this view, that people will vote 'no', and we must show them respect as well. I hope Melbourne can be an exemplar of that respectful debate."