Paul Stevens was forced into conversion therapy by the church when he was 15 after he told leaders he was gay.
"When you're a young person and you're developing your sense of identity if you have people who are telling you that you need to change something which is actually fundamental about who you are, it does do lasting damage."
The practice of trying to change a person's sexual orientation will be banned under the new law.
It will include religious groups, but they will still be able to freely express their beliefs.
An organisation which provides support to the rainbow community says conversion therapy takes many forms.
Aych McArdle from Outline said the law needs to clearly explain what is considered conversion therapy and what is not.
Conversion therapy can have significant, life-long impacts, McArdle said.
The bill will have its first reading in Parliament in early August and the Government aims to have the legislation passed by early next year.
- RNZ