Engaging in gay conversion therapy is to become a criminal offence in New Zealand after legislation received near unanimous support from lawmakers.

The ban makes conducting conversion therapy punishable by up to five years in prison. 

The law was passed by the New Zealand parliament on Tuesday, with 112 MPs voting in favour. 

Only eight MPs voted against the Conversion Practices Prohibition Legislation Bill, which was introduced to the parliament last year. 

"This is a great day for New Zealand's rainbow communities," Minister of Justice Kris Faafoi said.

"Conversion practices have no place in modern New Zealand."

Banning conversion therapy was one of the promises of Jacinda Ardern's Labour Party if it was re-elected two years ago. 

The New Zealand parliament's backing coincides with a new gay conversion therapy ban in the Australian state of Victoria. 

That ban came into force on Thursday and carries a prison sentence of up to 10 years.

It has been strongly opposed by evangelicals who fear that Christian parents risk going to jail unless they support their child's desire to transition.