''The next step … is having three people that love each other should be able to enter into a permanent union endorsed by society, or four people. There are even some creepy people out there, who say that it's OK to have consensual sexual relations between humans and animals. Will that be a future step?''

Senator Cory Bernardi. Credit:Andrew Meares

Labor Senator Helen Polley also spoke against the bill. She said two-thirds of the correspondence she had received on the issue had urged her to oppose change. She read aloud a letter from a constituent which said same-sex marriage could ''create another stolen generation by putting adult desires above the needs of children''.

But another Labor senator, Doug Cameron, said arguments about children being disadvantaged by being brought up be same-sex couples ''denies the reality of some children facing absolutely terrible lives with heterosexual couples''.

Labor Senator John Faulkner said the debate was not really about the value of marriage, or its role in society. ''It is a debate on the simple question of whether it is right for a government to deny some of its citizens access to a secular, government-recognised status on the basis of the gender of the person they choose to share their life with,'' he said.