The nation recorded its deadliest day of the pandemic on Monday with 19 people in Victoria succumbing to the disease.

Victoria's one-day total for new cases fell to 322 as the national death roll rose to 313.

Mr Morrison expressed his disgust at suggestions older Australians should have been "offered up" to the virus in order to reduce restrictions.

"That is just a hideous thought," he told reporters in Canberra.

"An absolutely amoral, hideous thought. One I have had no countenance with from the very first time it was suggested."

More than 200 people have died from coronavirus in the aged care system, a grim figure Mr Morrison described as a terrible tragedy.

Genomic testing indicates Victoria's botched hotel quarantine program could have sparked the state's deadly second outbreak.

Treasurer Josh Frydenberg renewed criticism of the Victorian government over significant failures in hotel quarantine, saying the mistakes must be explained.

Mr Frydenberg, who is self-isolating in Canberra ahead of federal parliament in two weeks, said it should never have reached the point where the state was recording high case numbers and multiple deaths a day.

"It's very very difficult emotionally, it's difficult obviously on the economy as well," he told 2GB radio.

"We know with respect to quarantine there have been very significant failures with deadly consequences. Victorians deserve answers. I'll leave that to Daniel Andrews and his government to provide."

It is not yet clear whether infections in Victoria's outbreak have peaked, although there have been encouraging signs in recent days.

Deputy Chief Medical Officer Michael Kidd said the past five days of declines were heartening, but urged caution around the figures.

"While we still have hundreds of cases being reported each day, we will continue to have people admitted to hospital and people becoming gravely unwell," he told reporters.

"Sadly some of those people will die."

Professor Kidd said Monday's deaths reflected high levels of community transmission from seven to 10 days ago.

Meanwhile, NSW has reported 14 new cases of the virus, including one with no known source.

Queensland recorded one new case of the virus overnight, a man in hotel quarantine who recently returned from overseas.

State authorities have opened up aged care homes to visitors, as they're now confident two infected teens who dodged quarantine did not spread the virus.

Australian Associated Press