'How does such evil happen in our land?' PM leads tributes to Hannah Clarke and her children

Hannah Clarke and her children were failed by Australia's domestic violence prevention system, Prime Minister Scott Morrison has declared.

The 31-year-old mother and her children were killed in Brisbane by Ms Clarke's estranged husband last week.

Mr Morrison has led tributes in Parliament, remembering Aaliyah, 6, Laianah, 4 and Trey, 3 as "joyous and wonderful children".

"That somebody could perpetrate that act, particularly as a father, it is incomprehensible," he said.

"An act of such depravity that only makes you ask — how does such evil happen in our land?"

The children's father, Rowan Baxter, doused Ms Clarke and the kids in petrol and set them alight before killing himself.

'This should not have happened'

The Prime Minister said Ms Clarke's family had "every right to be angry" that family violence services and policies did not prevent the tragedy.

He said all levels of government and courts needed to reflect on the murders and work to improve.

"We must reflect on how and where the system failed Hannah and her children, as it has failed so many others," he told Parliament.

"While this was the action of the depraved and evil man, we know enough of the circumstances leading up to the murders to know this should not have happened."

He said family violence would be on the agenda for the next meeting of state and territory leaders later this year.

A report in 2018 found one woman died every week due to the nation's domestic violence crisis.

"We must confront the awful truth that this is an epidemic," Opposition Leader Anthony Albanese told the Lower House.

Mr Albanese renewed his call for a national domestic violence prevention summit.

"We need to listen to those people who are impacted by family violence, and to the experts," he said.

"We need to learn. We need to desperately act."

More than $700 million has been committed over the past decade to Australia's national family violence prevention plan.

The Labor leader again rejected the Government's plan to merge the Family Court with the Federal Circuit Court.

"Whatever problems there are with the family law system, the existence of a standalone specialist Family Court is not one of them," he said.