Justice Minister Kris Faafoi says proposals to strengthen hate speech won't criminalise opinions or the "stupid" things people say unless they stir up hatred towards a particular group.

Faafoi also told Parliament's justice select committee this morning that a bill to repeal the three strikes law would be introduced "very soon", but Cabinet had yet to decide if second or third strike sentences would become more lenient once the law is axed.

Faafoi clashed repeatedly during the hearing with National Party justice spokesman Simon Bridges in ways that were both heated and comedic.

Changing hate speech laws was one of Labour's election promises, and the Government wants to extend protections from ethnic or racial groups to include those based on religious belief, sexual orientation, age or disability.

A Cabinet paper from December last year looked at moving hate speech offences into the Crimes Act and increasing penalties to up to three years' jail.

But instead of introducing a bill and getting feedback at select committee, Faafoi said public consultation on the proposals would take place "very soon".

Bridges asked if the Government wanted to "criminalise offensive, insulting, derogatory speech".

Faafoi replied that people were clearly entitled to their opinions and to say "stupid things".

"That is not what we're going to tackle ... but if that incites or stirs up hatred towards a particular group, that is the area we are going to put to the public about what should happen."

On three strikes, Bridges said that "apples for apples" the law had a deterrent effect, which had led to fewer second and third strike offences.

"Why are you changing this?"

Faafoi said there had been "no marked change in any of those types of offences" since the legislation was passed.

A Ministry of Justice report from December 2018 found the effect of three strikes was "inconclusive".

"Research in this area appears to be prone to political bias ... There have been no studies conducted on whether New Zealand's three strikes law reduces crime, although observations of crimes targeted by the law do not appear to demonstrate any obvious effects," the report said.

Between 1100 and 1500 people received a warning for a strike one offence every year.

For the past three years, about 100 people were convicted of a strike two offence, meaning they have to serve their sentence without parole. Most of the offences were for acts intended to cause injury, sexual assault and related offences, or robbery.

Last year seven people were convicted of a strike-three offence, meaning they had to serve the maximum sentence for that offence unless manifestly unjust. Three of them were for acts intended to cause injury.

Faafoi said Cabinet hadn't made any decisions on whether axing the law would see those serving a strike-two sentence become eligible for parole, or become able to serve less than the maximum sentence for a strike-three conviction.

Faafoi also defended Labour's election commitment to ban gay conversion therapy.

"People have the absolute right to choose their gender or sexual persuasion, and have the right to not have people try to change their fundamental human right to be who they are."

Bridges also asked Faafoi if he had ever talked to any judges about extradition cases, a question that was ruled out of order.

When Bridges challenged this, he was told by committee chair Ginny Andersen that he was "on thin ice".

"I'm not in any way on thin ice ... what standing order have I breached?" Bridges asked.

Faafoi answered the question anyway, saying even though he wasn't a lawyer, he was well aware that doing so would be inappropriate, given the separation of duties between the executive and the judiciary.

Bridges joked at the end of the hearing that he had more questions to ask "but I'm going to let you go".

Faafoi: "Thank you, your honour."