All of Australia's governments and the judiciary must reflect on how systems failed to protect Hannah Clarke and her children, Scott Morrison says.
The prime minister was speaking in federal parliament on Monday, less than a week after Ms Clarke was murdered by her estranged husband Rowan Baxter, along with their three children.
Mr Morrison said the country sends its love to those grieving the family, stressing they have a right to be furious about the "terrible crime".
"Everything we have done across this country to protect women and children didn't protect Hannah and her children from this evil," he said.
"I believe state, territory and national governments, all of us, and our agencies and importantly the judiciary, we must all reflect again on these terrible murders.
"We must reflect on how and where the system failed Hannah and her children, as it has failed so many others. It is so frustrating. It's so devastating."
The prime minister said enough is known about the circumstances of the murders to know that they "should not have happened" and a Queensland inquest into the deaths will reveal the truth.
"Hannah deserved to feel safe and be safe, and to watch her joyous and wonderful children grow up. And Aaliyah and Laianah and Trey deserved to have a childhood that was innocent, and to have lives that were long and joyous."
Opposition Leader Anthony Albanese said the nation must confront the awful truth that domestic violence is an epidemic, with an average of one woman a week murdered by her current or former partner.
He reiterated his call for a national domestic violence summit.
"The memory of Hannah Clarke and her three beautiful children must galvanise us all into further action to eliminate violence against women and children," he told parliament.
"We can't accept this is normal. We have it in us to be so much better. Lives depend on it, as we see all too often.
Party leaders in the Senate also reflected on the murders, with One Nation leader Pauline Hanson saying Baxter had committed the "ultimate act of betrayal".
His "disgusting action" has further added fuel to an already difficult debate about family law which has "seen many decent men deprived of their parental rights", the senator added.
"Please do not let this bastard's action reflect on all men," she said.
Centre Alliance senator Rex Patrick will seek to establish an urgent Senate inquiry to pressure all levels of Australian government to take further action to prevent violence against women and children.
"We all need to bang on the doors of government to demand real action," he said in a statement.
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