Christian groups in Australia are expressing concerns that new legislation proposed in the nation's most populous state could have dire consequences for religious freedom, and see parents, pastors, and healthcare workers face criminal charges for providing non-affirming care for those who are confused about their sex.

While the ostensible purpose of the New South Wales legislation is to introduce bans on so-called conversion therapy relating to sexual orientation and gender identity, the Australian Christian Lobby (ACL) has warned that a draft of the bill recently leaked in a major news outlet suggests a risk that it could prevent free expression of Christian beliefs and teachings on the topic.

"There is a danger that NSW parents could lose the legal right to discuss issues of sex and sexuality with their children under new conversion practices legislation," ACL said.

The lobby said that the leaked pages of the Bill showed a marked divergence from initial descriptions of the legislation, and demonstrated that the newly elected Labor government was reneging on its pre-election promises to ensure protections for freedom of religious belief.

ACL said that some of the possible consequences of the bill could include medical professionals being unable to challenge an "affirmation" based approach at the expense of medical best practice.

The lobby group also warned it could potentially see parents prosecuted for advising their gender-confused child against undergoing medical reassignment procedures, or even prohibit pastors or churchgoers from directly pastoring to, or praying for, a congregant on matters of sexuality.

"These developments are alarming. Those who experience gender incongruence, especially children and young adults, are some of the most vulnerable in our society," ACL said.

"We must respond promptly and pressure the new [Labor] government to provide specific protections for parents, pastors and medical professionals to ensure the safety of our children and the freedom to uphold a biblical view of sex and sexuality."