Victim Support chief executive Kevin Tso said the reforms had the potential to be a "game changer" for family violence victims.
"In particular, Victim Support welcomes a renewed focus on services to victims and to early intervention," he said.
"Above everything, the most important things we can do for victims are ensure there are clear steps to prevent reoffending, and that quality support services are available to stay physically and mentally safe and navigate the justice system."
Tso said resources needed to be prioritised for frontline services.
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Women's Refuge said the changes were a "giant step" in the right direction. The Human Rights Commission hailed them as "very positive".
"This comprehensive overhaul has been long overdue," Equal Employment Opportunities Commissioner Dr Jackie Blue said.
"Family violence remains a major human rights challenge facing thousands of New Zealanders, impacting families from all cultures, classes, backgrounds and socio-economic circumstances ...
"I'm particularly pleased to see that coercion to marry will now be an offence under legislation."
Plunket also welcomed the new laws, saying children thrived when people around them were in positive, non-violent relationships.
"Even if the abuser is not directly violent to the children, children may be seriously affected by seeing or hearing their parent being hurt," Plunket general manager of clinical services Helen Connors said.
Key called on perpetrators to recognise what was going on in their home and take responsibility for it.
"A good father, a good stepfather and a good man does not hit, intimidate or control his spouse, partner, ex-partner or her children. The same goes for women who are abusers.
"If you act in a violent and controlling way, you can change this behaviour. Own the problem. Nothing will get better until you do. Ask for help. There is no shame in that."
Jane Drumm, of the domestic abuse charity Shine, said she had never heard a Prime Minister speak so strongly about the issue.
"I have been doing this work now ... for 33 years, and I have never in all that time heard such a strong statement from a politician."
Nearly 500 detailed submissions were made by individuals and groups after the Government released a discussion document last August.
Legislation is expected to be introduced to Parliament early next year.
Key changes
• Allowing others to apply for a protection order on a victim's behalf, and better providing for the rights of children under protection orders.
• Making offending while on a protection order a specific aggravating factor in sentencing.
• Letting people refer themselves to services to help stop violence, such as giving the perpetrator access to non-violence programmes, without their having to go to court.
• Make it easier for the sharing of information between the courts, police and the agencies and community organisations that deal with families.
If you're in danger NOW:
• Phone the police on 111 or ask neighbours of friends to ring for you
• Run outside and head for where there are other people
• Scream for help so that your neighbours can hear you
• Take the children with you
• Don't stop to get anything else
• If you are being abused, remember it's not your fault. Violence is never okay
Where to go for help or more information:
• Women's Refuge: Free national crisisline operates 24/7 - 0800 REFUGE or 0800 733 843 www.womensrefuge.org.nz
• Shine, free national helpline 9am- 11pm every day - 0508 744 633 www.2shine.org.nz
• It's Not Ok: Information line 0800 456 450 www.areyouok.org.nz
• Shakti: Providing specialist cultural services for African, Asian and Middle Eastern women and their children. Crisisline 24/7 0800 742 584
• Ministry of Justice: www.justice.govt.nz/family-justice/domestic-violence
• National Network of Stopping Violence: www.nnsvs.org.nz
• White Ribbon: Aiming to eliminate men's violence towards women, focusing this year on sexual violence and the issue of consent. www.whiteribbon.org.nz