A report prepared for the project by former Children's Commissioner Cindy Kiro has found that this over-representation of Maori is mainly because of their poverty.
Dr Kiro has recommended "early and effective intervention" in a way which "builds on respectful relationships with whanau".
Ms Fletcher said her social workers would aim to work on socio-economic factors, such as helping families to find work and good housing, and cultural factors such as reconnecting with their whakapapa or wider family heritage.
"We have to address a growing underclass within the Maori communities, which is where we are seeing the worst in terms of family violence and child abuse," she said.
"The research goes back historically in terms of urbanisation of the Maori community and how that [cultural] disconnection and poverty and all those things are contributing to what is a growing underclass."
She said male offenders would continue to be directed to men's programmes run by Man Alive in Henderson, but the new service recognised that 90 per cent of women who were the victims of family violence wanted to stay in their relationships.
"We have to work with them as a couple, work with their relationship, and get both of them to focus on to their relationships with their children as a way of change."