Brisbane's Catholic archbishop has cited society's refusal to accept the marriage of parents to their children in urging Australians to vote no to same-sex marriage.
Archbishop Mark Coleridge has also said that while the love of same-sex couples is valuable, it's "like the love of friends".
He's says human societies have "always discriminated in deciding who can marry whom".
"I mean parents can't marry their children. Children can't marry their parents," he told the ABC on Tuesday.
He said siblings could not marry each other, and underage people and same-sex couples had also been "disqualified" from marrying.
"That is not to say that they are not equal. It's simply saying they are not the same, and that they don't qualify for what we call marriage."
The comments echo those he made in a position statement on same-sex marriage, released earlier this month as the federal government prepared to launch its postal survey on marriage reform.
In that piece, he wrote that all human beings are equal "but that doesn't mean they are the same".
"Same-sex marriage ideology implies that equality means sameness. But it doesn't."
"They understand that this is about giving a fair go to all": Alex Greenwich responds on Sky News to comments made by Archbishop Coleridge. Source: Sky News image grab
'Deeply offensive'
Marriage Equality Australia Co-Chair Alex Greenwich told Sky News that Archbishop Coleridge's comments were "deeply offensive," and encouraged him to consult with other religious leaders who support marriage equality in Australia.
'I would hope that he speak to the bishop of Parramatta or the bishop of Newcastle or the New South Wales Jewish board of deputies or the 500 clergy across Australia who support marriage equality," Mr Greenwich told Sky News.
"They understand that this is about giving a fair go to all and understand the importance of marriage to all couples gay or straight."
Abbotts divided
Former prime minister Tony Abbott, a staunch Catholic, has also urged Australians to vote 'no' to "protect the family" and says they should view the survey as a vote against political correctness.
Mr Abbott's daughter, Frances, is featuring in a vote 'yes' campaign video, in which she says marriage equality will make society less lonely for many people.
Ms Abbott talks about her aunt Christine Forster and how she hopes to be part of her same-sex wedding one day.
"To see aunty Chris marry Virginia, to do it here in front of friends of family, it would be so special and I'm so, so hoping that's something that I get to be a part of," she said.
Ms Forster, a Liberal councillor for the City of Sydney, is campaigning against her brother on the issue.
