Liberal Senator Cory Bernardi's remarks that allowing same-sex marriage would lead to demands to legalise bestiality and polygamy have been slammed by gay rights lobby groups and politicians.
Senator Bernardi is expected to be called into Tony Abbott's office today and asked to explain himself.
With Labor demanding this morning that Mr Abbott sack Mr Bernardi from his position as shadow parliamentary secretary to the Opposition leader, senior Coalition sources say Senator Bernardi ''will be spoken to'' but were unsure of what, if any action would be taken.
Speaking in Parliament last night on a gay marriage bill sponsored by four Labor senators, Senator Bernardi said the push for same-sex marriage was part of an attack on ''our enduring institutions''.
''It is another chip in the fabric of our social mores,'' he said. ''The time has come to ask, when will it end? If we are prepared to redefine marriage ... what is the next step?''
''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?''
Liberal frontbencher Joe Hockey has called for a ''measured and sensitive'' debate and Greens Senator Richard Di Natale describing the remarks as "offensive and appalling".
Australian Marriage Equality convener Alex Greenwich said Senator Bernardi's comments were extremely predictable, and taken straight from the "American religious right play book".
"It's based on fear, not on facts," Mr Greenwich said. "There is no international example that backs up what he's saying.
"The comments are highly offensive to the tens of thousands of loving and committed same-sex couples who just want to marry."
Judy Brown, the president of Parents, Families and Friends of Lesbians and Gays New South Wales, agreed Senator Bernardi's remarks were "terribly offensive".
She said those kinds of comments did not make it easier for young gay people, who might be suffering depression and anxiety at the thought of coming out.
"[They are not suffering depression] because of the fact they're gay. Really it's just that they're treated so badly and they have to suffer all this adversity."
Senator Di Natale said: ''What an affront to those parents whose kids are struggling with their sexuality, who are suffering from anxiety and depression and self-harming because their kids' choices around sexuality are being compared to bestiality. What an appalling, appalling statement from somebody whose standards in the Parliament need to lift."
Mr Greenwich said Senator Bernardi's remarks were far removed from the views of most Australians.
"What is encouraging to us is that a strong majority of Australians reject the kind of prejudice that Cory Bernardi is trying to peddle.
"They know that this debate is about families, equality and love and, obviously, gay and lesbian Australians know we've got the majority of Australians on our side."
Mrs Brown said same-sex couples should have the same human rights as heterosexual couples.
"Our son has been with his partner for eight years ... and I just think it's an abuse of their basic human rights that they're treated as second-class citizens."
She said while the general attitude towards homosexuality had improved and laws giving same-sex couples greater financial equality had been passed, the issue of same-sex marriage had to be resolved.
"Still not having same-sex marriage means that they feel their relationship and their love is not considered to be equal to their heterosexual brothers and sisters."
