A New South Wales parliamentary inquiry that was sparked by a gruesome murder case has recommended placing strong restrictions on the partial defence of provocation.

The inquiry was launched after Sydney man Chamanjot Singh was sentenced to just six years in prison for repeatedly slitting his wife's throat with a box cutter.

He had successfully argued that he had been provoked because she had told him she was in love with someone else and threatened to have him deported.

Committee member Nationals MP Trevor Khan says it was a clear case of the defence being misused.

"The use of deadly force against women in the circumstances of the breakdown of a relationship cannot be acceptable," he said.

The inquiry is recommending keeping the defence, so it can still be used by long-term victims of domestic violence, but restricting it to cases where conduct has been "grossly provocative".

Committee member and Greens MP David Shoebridge says the inquiry was convinced there were good reasons to keep the defence.

"We had very compelling evidence that the defence of provocation serves an essential part in the criminal justice system, which was really for protecting mainly women who have been subject to ongoing domestic violence," he said.

"In the most extreme examples of that, where there's been ongoing belittlement, on going violence, then in those circumstances there does need to be a safety valve in the law."

The committee is also recommending the law spell out certain circumstances where the defence should not be allowed, such as in response to a non-violent sexual advance or the infidelity of a partner.