"But we want people to know that there is help out there."
The characteristics of family violence meant children were often exposed to it, or were experiencing the abuse themselves, Mr Crawley said.
"Either way, children living in violent environments are the most vulnerable victims."
It took courage for victims to ask for help, but it was an important first step, he said.
Police worked closely with support agencies such as Women's Refuge and help was available 24 hours a day, seven days a week.
If people thought someone they knew might be the victim of abuse or the abuser, they needed to step in and let them know it was not okay, Mr Crawley said.
"Sometimes it takes someone on the outside to spark a change."
There were programmes in the community to help victims and perpetrators of violence.
"We are committed to ensuring that all reported episodes of family violence are investigated, and followed up with the right course of action."
Nationwide, 69 per cent of offenders in the 2313 acts intended to cause injury this June were known to their victims and in 44 per cent of cases the offenders and victims were family.
Victims were known to their offenders in 38 per cent of New Zealand's 21 homicide and related offences this June. In two cases, the victim and offender were family.
In 9 per cent of New Zealand's 558 burglary cases this June, the victims knew the offenders. In six cases, they were family.
Women's Refuge chief executive Dr Ang Jury said police believed they saw only about 20 per cent of family violence cases.
"To encourage more reporting we need to have victims convinced that they're going to be treated seriously when they do report and that something's going to happen."
Those concerned about relationships with family and friends should talk with police or an agency such as Women's Refuge.
"Family violence, in particular, thrives best in silence and in secrecy," said Dr Jury.
Victim Support service delivery general manager, Angela Crawford said it was a "very sad fact" that so many offenders were known to their victims.
Victim Support tried to market itself so people knew they were just a free and confidential phone call away, she said.
Victim Support assesses danger and needs and advises victims of the best steps to take. It could also listen, provide information, refer victims to counselling services and help with police and court processes.