Gay Labour MP and former lawyer Charles Chauvel is spearheading a bid to remove provocation as a defence in criminal cases.

The defence is often used in court by defendants to justify violent attacks if provoked by a victim. But now Mr Chauvel has drafted a bill to get the defence of provocation removed.

It was an "aspect of our criminal law which provides justification for lashing out and violence against people," he told the website.

The partial defence of provocation "lets people know they can get away with murder, and it's time we did away with the provision".

The Law Commission released a report in 2007 which said the partial defence of provocation should be abolished.

The report said the partial defence of provocation is "irretrievably flawed" because it claims to be a partial excuse, assumes there can be a loss of self-control, and that in extreme circumstances an ordinary person, when provoked, will resort to homicidal violence.

The move comes amid anger in the gay community over the case of a Hungarian tourist who bashed a man to death.

Ferdinand Ambach, 32, a dive master, was found not guilty of murdering Ronald Brown, 69, but guilty of manslaughter. He faces a maximum penalty of life imprisonment when he is sentenced next month.

During a High Court trial in Auckland, the jury was told that Ambach beat Mr Brown with a banjo before ramming the instrument's neck down his throat.

The attack happened after Mr Brown met Ambach in a bar and took him back to his Onehunga flat. Part of Ambach's defence was that Mr Brown, who was gay, made unwanted sexual advances to him.

At the trial, defence lawyer Peter Kay raised the possibility that Mr Brown might have attempted to rape Ambach, which triggered "a monstrous rage" during which Ambach lost control.

Gay rights advocate Neville Creighton said he could understand the jury's conclusion of manslaughter, as it appeared that there had not been evidence of premeditation.

But the gay community would want a sentence that reflected the seriousness of the attack.

Mr Creighton drew a comparison with a heterosexual situation.

"If this sort of panic is an acceptable defence, then every woman who has an unacceptable advance made to her would have a right to attack and kill the guy, which is patently stupid," he said.

"This was a strong, young guy with a much older man. If he had to be physical, why didn't he just punch him once and walk out?"

Mr Brown's family condemned the provocation law that allowed a partial defence of murder, with niece Tracy Evans saying they were "deeply disgusted with the verdict".