Marriage equality will increase gender confusion because it undermines the “complementarity” of males and females, the Australian Christian Lobby has said.

ACL makes the claim in submissions to the Senate committee examining the government’s marriage equality bill exposure draft, in which it argues marriage is a “child-centric” institution and calls for changes to allow discrimination against same-sex couples on the grounds of freedom of religion.

The bill, released before the Senate vote blocking the government’s proposed plebiscite, would allow civil celebrants and religious organisations to refuse to provide goods and services to gay weddings.

LGBTI rights groups, including Australian Marriage Equality and Just Equal, have called to remove those exemptions and warned that allowing for practices based on “conscientious belief” could open the door to discrimination on other grounds, including race.

ACL argued that freedom of religion is a fundamental right that protects both individuals’ beliefs and practices. It approved the exposure draft’s plan to allow civil celebrants to refuse to perform same-sex weddings and advocated that providers of goods of services including bakers and florists should have the same right.

ACL rejected the idea marriage equality is a right guaranteed by the principle of equality before the law, arguing restricting marriage to a man and a woman is a just form of discrimination because marriage is “child-centric”.

“If marriage is a child-centred institution it reasonably follows that [it] is not a category of relationship that can reasonably apply to same-sex relationships, which do not bear even the possibility of producing children,” it said.

In November the Australian human rights commissioner, Ed Santow, told Guardian Australia the “better view” was that the principles in international law of non-discrimination and equality before the law demanded that civil marriage be extended beyond heterosexual couples.

ACL claimed that same-sex marriage would “inevitably” result in children “who are deprived of the right to be known by and raised by their parents” without identifying how the proposed marriage law affects children of same-sex couples, many of who were already parents.

It said marriage equality would affect gender norms because “the complementarity of male and female is uniquely defined in the marriage law”.

“Where gender is erased from the fundamental group unit of society, it logically follows that gender becomes increasingly confused at all levels in the community.”

ACL called to extend a range of discrimination law exemptions so that all wedding service providers, not just religious organisations, could discriminate on the basis of “sincerely held conscientious or religious beliefs about marriage, family, sexuality and/or gender”.

It said people who define marriage as between a man and a woman should not be discriminated against in a range of spheres, including employment, advocating that even government employees of registry offices should be able to refuse to register gay weddings.

In separate submissions Australian Marriage Equality, veteran LGBTI rights campaigner Rodney Croome and Just Equal argued that religious freedom was adequately protected by the draft bill’s provision allowing ministers of religion to refuse to perform weddings.

AME and Just Equal said that since civil celebrants conduct weddings on behalf of the state, they should not be allowed to refuse to wed same-sex couples.

AME suggested the bill should specify that ministers of religion only be allowed to refuse weddings on the basis of religious doctrine or beliefs and not the new category of “conscientious beliefs”.

It warned the concept of exemptions based on “conscientious beliefs” could undermine discrimination law in other contexts including commercial services, education or health and even be used to justify discrimination on the basis of other attributes like age, sex, race and religion.

Just Equal argued: “If this parliament accepts that same-sex couples can be discriminated against because of the religious beliefs of service providers, what stops a future parliament allowing discrimination against inter-racial partners, inter-faith partners, civil union partners, or any partners who don’t conform to a particular religious doctrine?”

AME argued the right to freedom of belief is absolute but the right to freedom of conduct based on those beliefs is not. It said new exemptions for “religious organisations or bodies” to refuse to provide services to gay weddings should be removed or at least more clearly defined.

Just Equal similarly argued against discrimination law exemptions for religious organisations that provide commercial services, warning that gay couples in rural and regional areas may struggle to find service providers as a result.

Croome submitted that allowing religious service providers to refuse gay weddings “perpetuated prejudice against LGBTI people”.

“Overwhelmingly, contemporary Australians would look with disgust at a sign declaring ‘NO BLACKS’ or ‘NO ASIANS’,” he said. “We must not allow anyone to feel it is legitimate to display a sign declaring ‘NO GAYS’ or, in absence of such a sign, do anything tantamount to such an exclusion.”

Submissions to the Senate inquiry closed on Friday. Its report on the government’s exposure draft is due by 13 February.