Prime Minister Scott Morrison says all levels of government and the judiciary must reflect on how systems failed to protect Hannah Clarke and her children.
Mr Morrison promised to take action to combat domestic violence, less than a week after Ms Clarke was murdered by her estranged husband along with their three children.
“There are never any excuses - there are none - or justifications for the evil that Hannah and her children experienced - never - not under any circumstances,” Mr Morrison told Parliament.
Hannah Baxter is being remembered as a "beautiful soul". Source: Facebook
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."
His speech made no specific commitments, but he said he would raise the matter when state and territory government leaders meet at COAG in a few weeks time.
Ms Clarke died after her estranged husband, Rowan Baxter, doused her in petrol and set the car they were travelling in alight in Brisbane's east.
Her children Aaliyah, 6, Laianah, 4, and Trey, 3, died in the car fire.
The death of a Townsville woman, who was stabbed to death in her home the same week, intensified calls for stronger action against domestic violence.
'These things happen'
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.
One Nation leader Pauline Hanson is threatening to take the Queensland Government to court. Source: AAP
Earlier, Senator Hanson commented about the family's murder on the Today show, suggesting Baxter may have been "driven to it".
"Don't bastardise all men out there, or women for that matter, because these things happen," she said.
On average one woman a week in Australia dies by domestic violence.
Opposition leader Anthony Albanese said domestic violence must be called out, describing the death of Ms Clarke’s family as “beyond comprehension”.
“We must confront the awful truth that this is an epidemic,” he said.
"Everyone is affected by this scourge … we cannot be mere bystanders.”
He reiterated Labor's calls for a national summit on domestic violence to bring together experts and survivors of domestic violence.
The prime minister said $840 million had been committed to addressing domestic and family violence since 2013.
But he said work cannot stop until all those facing in the same danger as Ms Clarke and her children are protected.
Earlier, Greens Senator Larissa Waters had questioned the prime minister’s response, arguing more funds were needed.
“What we really need is for the PM to stump up the funding for frontline services so they don’t need to turn any women or children away when they seek help,” she said.
“Thoughts and prayers are not going to cut it.”
Additional reporting by AAP