A woman in her 80s has become the latest death after her body was found in her flooded Lismore home on Tuesday.
Eight people have died in Queensland.
The Australian Defence Force has rescued 74 people and sent 600 personnel to assist with rescue operations.
Ten helicopters and a Poseidon aircraft have also been deployed.
Prime Minister Scott Morrison said more personnel were being mobilised, with heavy rain expected for the NSW south coast, East Gippsland in Victoria, and northern Tasmania.
"I want to assure people … at the same time as we're preparing the response (to the floods), we are already preparing - together with the state and local governments - the recovery and clean-up operation," Mr Morrison said in Canberra on Tuesday.
"Assets have been pre-positioned and planning is underway."
The prime minister said any further requests for federal assistance from the NSW and Queensland governments would be provided "immediately".
Mr Morrison said 35 local government areas have been activated for disaster support, and some 80,000 disaster payment claims had already been made.
He said Services Australia teams would be available in evacuation centres to help people submit claims.
Opposition Leader Anthony Albanese said the country was witnessing "the best of Australia at the worst of times".
However, he said the government needed to do more.
"We need to cut through the bureaucracy and make sure that the services are given where they are needed and when they are needed, which is right now," he said.
Mr Albanese said it was "beyond comprehension" a $4 billion emergency response fund set up by the government had not been spent on preparing for disasters.
"(The government) set up a fund a few years ago. We supported that happening. It got $800 million of interest, it's now bigger than it was at the beginning," he told Brisbane radio B105.
"We need to make sure that we prepare for disasters in advance and spend the money that's been allocated."
Labor has committed to establishing a disaster-ready fund and would spend $200 million a year on natural disaster prevention and readiness if elected.
Emergency Management Minister Bridget McKenzie says the government's funding is operating as intended, with $50 million annually going towards flood mitigation projects.
"The emergency response fund was set up as a future fund to be used when all other sources of funding have been exhausted ... it's there for the future for communities - long after I'm the minister - to be able to exercise and use," she told ABC television.
"We're focused on getting people safe, making sure that they're alive and have that immediate support, and then we have the long road to recovery."
The weather system is expected to move further down the east coast.
Emergency Management Australia and the National Disaster Recovery and Resilience Agency held a national coordinating mechanism meeting on Tuesday afternoon with the states and territories.
The meeting is understood to have canvassed issues including supply chains, electricity, communications and roads.
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