A national Christian group is lobbying for the Disability Discrimination Act to be changed so that it can discriminate against people with mental illnesses, on the basis they could upset the "sacred" nature of church services.

FamilyVoice has called for a religious exemption to the Act, arguing it interferes with freedom of religion.

In a submission to a federal parliamentary inquiry on freedom of belief, FamilyVoice said a person with a mental illness had the potential to interfere with a church service.

"For very good reasons a religion may not wish to engage a person who has a mental illness and displays disturbed behaviour," the submission read.

"Such behaviour would adversely affect a church service, which is sacred in nature.

"A simple provision should be added for an exemption from the act for persons ... whose conscientious beliefs do not allow them to comply."

Problematic behaviours the issue, not disability: group

FamilyVoice national director Ashley Saunders took over leadership of the group last year. ( Supplied: FamilyVoice )

FamilyVoice national director Ashley Saunders "strongly repudiated" any suggestion the group did not want to support people with mental illness or disability.

"Our submission did not say we should be able to discriminate with a blank canvas in areas of mental disability," Rev Saunders said.

"It is appropriate in some circumstances to discriminate justifiably where the person is involved in disturbed behaviour that is contrary to the best interests of the organisation.

"Nowhere does the submission say that we don't want people with disturbed behaviour to be part of a church.

"What we have said is that church organisations should be able, in making decisions about employment, who leads the service, it is entirely appropriate that people who fulfil those roles not be people who manifest disturbed behaviour."

In an earlier statement, he said "we have absolutely no desire to exclude disabled persons" and "our policy submission raises concerns about problematic behaviours, not disability status".

"We hold the view that it would be most unhelpful if a religious organisation had no option but to engage someone in a public role who (for example) struggled with uncontrollable urges to loudly vocalise profanity or sexually explicit phraseology that would upset family worship services," he said.

"I hasten to point out that our staff members have a very long and positive association with people who have quite serious mental health challenges."

'Dangerous stereotype' will isolate people

South Australian Dignity Party MLC Kelly Vincent said the group's submission was "cruel" and "hypocritical".

"I think this is not only incredibly shaky legal ground, it is also very cruel and ignorant," Ms Vincent said.

"It sends a very dangerous stereotype that all people with mental illness exhibit these behaviours, are dangerous somehow or want to interrupt services.

"Everyone knows that Jesus was seen as a friend of the underdog and protector of the underprivileged, so I think this is a very cruel and hypocritical move.

"If you are isolating someone, particularly with mental illness, from receiving services and participating in a community activity like church or religious services, you are only going to compound those feelings of isolation and negative feelings that can lead to further mental illness."

She said people needed support.

"The vast majority of people with mental health challenges can lead very productive, peaceful lives, especially if we have the right support around us, and for some people that may include church services," she said.

Ms Vincent said not employing people because they had a mental illness could lead to the "best people", who had managed during hard times, not being available to teach valuable lessons.

"As long as they can perform the duty of the job, who better to do that than someone who has experienced those difficult times?" she said.

FamilyVoice says sex change 'delusional'

FamilyVoice, which is an Adelaide-based national Christian organisation, also wants the Sex Discrimination Act changed, stating the laws as they stood directly contradicted the moral values of the Christian faith.

The Sex Discrimination Act bans the discrimination of people on the grounds of sexual orientation, gender identity and relationship status.

FamilyVoice has described these matters as "highly controversial", and in its submission called sex change "delusional".

"The reality is that 'sex change' is a myth. Neither hormone treatment nor surgery can actually change a person's sex," the submission said.

Conflict over the anti-discrimination laws is "almost inevitable", according the submission.

"The effect of the Act is to empower those who have espoused one value system to impose their beliefs on those with contrary beliefs," it said.

"Far from fostering social harmony, the Act is likely to exacerbate social divisions."

The group's social media accounts show FamilyVoice takes a stance against same-sex marriage, transgender people, abortion, euthanasia and unisex bathrooms.