As Federal Government ministers publicly vent their disagreements over the issue, the Opposition Leader has also jumped in with his thoughts on those arguments.
But, separately, the Labor leader has now had to fend off questions about his past as a dual citizen.
Former champion swimmer Ian Thorpe has become the face for the "yes" campaign in the same-sex marriage debate.
The five-time Olympic gold medallist appears alongside his partner, Ryan Channing, in a video by the campaign group Australian Marriage Equality.
"If you support marriage equality, you need to enrol to vote or update your details by midnight, August 24. You can do that online. And I've bet Ryan that I can do it faster than he can swim a hundred metres. Go!"
With only days to go until the deadline to update personal details or enrol to vote in the same-sex marriage survey, the battlelines are being drawn.
The chief executive of Qantas, Alan Joyce, has told reporters in Sydney his airline will also join the "yes" campaign.
"I will be out there strongly campaigning for a 'yes' vote. I think it is very important for our employees, four customers and for our shareholders, and that's why Qantas is a supporter of marriage equality."
But there are prominent supporters of the "no" campaign, too.
Former prime minister Tony Abbott has become one of the strongest voices campaigning for Australians to vote no in the planned postal survey.
If it survives a High Court challenge, the ballot forms are meant to be sent out from September 12, with the final result being announced in November.
Mr Abbott has voiced his opposition on Sydney's 2GB Radio.
"This isn't just about marriage. Sure, marriage is the immediate focus. But there are lots and lots of implications here, and we've got to think them through before we take this big leap into what, I think, is the dark."
He warns schools, hospitals, charities and welfare agencies would be vulnerable to challenge if the "yes" campaign succeeds.
And he is not backing down from his claim the same-sex marriage survey will affect other social issues.
"If you de-gender marriage, a whole lot of other things come in its wake. How, for instance, can we legitimately say no to gender-fluidity programs like so-called Safe Schools if we've de-gendered marriage? If we have officially sanctioned de-gendering marriage, it's very hard not to see de-gendering come in in so many other areas as well."
It is a line of argument Attorney-General George Brandis dismissed on Sky News on Sunday, a sign of the frustration among Liberals who support same-sex marriage.
"What I am not going to do is be tricked by Tony Abbott and others who are trying to turn a debate about one issue into a broader debate about religious freedom."
Junior Liberal ministers Zed Seselja and Angus Taylor have publicly backed the former prime minister.
But Opposition Leader Bill Shorten has dismissed their claims, too.
"Do you support marriage equality or not? All of the other issues being raised by those who are against marriage equality are other issues. This statistical survey changes nothing about your ability to go to church or religious freedom, let's be straight about that, let's be unequivocal. It is a distraction."
But the Labor leader has not escaped scrutiny of his own.
The unpredictable citizenship saga has already put the careers of seven politicians in doubt, including Deputy Prime Minister Barnaby Joyce.
If the High Court rules Mr Joyce was illegally elected because of his dual New Zealand citizenship, the Government's slim majority in the lower house will be threatened.
The Government is now claiming Bill Shorten should prove he also is not a dual British citizen, a point he says is clearly decided.
"I am fully aware that the Government is desperately trying to peddle its newest conspiracy that I'm a secret English agent. You know, the reality is that, no, I'm not. I renounced my citizenship in 2006."
Mr Shorten says he will not publicly release his renunciation documents and he does not have to.
He says Labor's eligibility processes are rigorous and no party member should have to publicly prove they have renounced dual citizenship.
"So let's be straight here. This is a Government desperate to distract attention away from the fact that not one but two of their senior ministers have a cloud over their constitutional eligibility, including the Deputy Prime Minister."
The High Court will begin hearing the case of Barnaby Joyce on Thursday.
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