The New South Wales Government is introducing the new offence of "strangulation" in an attempt to reduce domestic murders.

Key points: Strangulation is a factor in a quarter of domestic murders in NSW

Strangulation is a factor in a quarter of domestic murders in NSW The length of apprehended domestic violence orders will also be increased

The length of apprehended domestic violence orders will also be increased If passed, the changes will come into effect later this year

Only half of the 600 cases involving strangulation that have gone to court since 2014 resulted in convictions because the offence is often hard to prove.

Minister for Family and Community Services Pru Goward said strangulation was a factor in a quarter of all domestic murders.

"To treat strangulation seriously, because it's such a strong indicator of a likelihood of a fatal attack, it's been important to reform the laws regarding strangulation, and that's what we've done," she said.

The NSW Government expects the change will come into effect this year.

The next year, the NSW Government will increase the length of time apprehended domestic violence orders (ADVOs) remain in force, from one to two years.

Courts will also be empowered to make orders permanent in exceptional circumstances.

Police will be given a new power to vary ADVOs between court appearances to protect victims.

Attorney-General Mark Speakman said: "Even if someone doesn't get a final ADVO straight away, they can get a provisional ADVO from police … pretty quickly, so there is no gap in protection of victims."

Ms Goward said there had been a significant reduction in the rate of victimisation and domestic violence in New South Wales.

"In particular there's been a 15.5 per cent reduction in domestic violence-related grievous bodily harm," she said.

"We are the only state to have recorded such a reduction … that I think is an indicator that the determination of the Government and the community has paid early dividends, but there is more work to do."