The defence of provocation is one step closer to being erased from the statute books.

The Crimes Provocation Repeal Amendment Bill unanimously passed its first reading in Parliament last night.

The issue has been in the spotlight recently after Otago University tutor Clayton Weatherston argued he stabbed girlfriend Sophie Elliott 216 times because he was provoked and should be found guilty of manslaughter rather than murder on those grounds.

The jury convicted him of murder.

In an earlier case, provocation was successfully used as a defence by Ferdinand Ambach, who killed Auckland man Ronald Brown.

Ambach argued he lost control and rammed the stem of a banjo down Mr Brown's throat because the older man was coming on to him strongly and Ambach feared he would be raped.

Last night, Justice Minister Simon Power told MPs the partial defence is fundamentally flawed because it rewards a lack of self control by enabling an intentional killing to be categorised as something other than murder.

He said allowing anger to be singled out as a mitigating factor is not in line with the message that people must find ways other than violence to manage their anger.

Mr Power says there are also concerns about an accused's ability to tarnish a victim';s character, when the victim cannot defend themselves.

However, Green Party MP Kevin Hague, who has long advocated for gay rights, told MPs they have to take a stand for gay men to be able to love and live without discrimination.

He says sending the signal that violently taking the life of a gay man is of less consequence than taking the life of another is obnoxious in the extreme.

Repeal of the partial defence would make factors such as the alleged sexual behaviour of the victim less relevant at the trial.