More than half of Australian aged care residents live in facilities with a one or two star rating according to research from the University of Wollongong.
Researchers from the Australian Health Services Research Institute, based at UOW, used a five-star rating of staffing levels from the US which they refined for Australian conditions.
Their report - commissioned by the Royal Commission into Aged Care - found 57.6 per cent of residents were in homes with "unacceptable levels of staffing" or one or two stars.
Meantime 27 per cent of Australians were in homes with "acceptable" staffing levels, or three stars; and 14.1 per cent were in four-star facilities with good staffing levels. Just 1.3 per were in five-star homes which represented 'best practice' in terms of staffing.
The report authors said to raise the standard so all residents received at least a three-star level of staffing - those homes rated one or two stars would have to increase staff numbers by more than a third.
That would result in an overall increase of 20 per cent in total care staffing across the nation.
"A recurring theme in the evidence presented to the Commission has been that the staffing levels and skill mix within aged care has been insufficient to support quality outcomes for residents," the report stated.
The paper also outlined how the aged care sector had evolved in recent decades - with residential services moving away from institutionalised to more person-centred models of care.
Expansion of community aged care services that enabled older people to stay in their own homes longer had also resulted in people with much higher, more complex care needs by the time they entered residential care.
The current Aged Care Funding Instrument did not "sufficiently discriminate between levels of need" so did not provide a basis on which to determine appropriate staffing levels.
"It is clear from this analysis and the evidence being presented to the Commission that there is a need for additional investment in care funding, the majority of which is required to increase staffing levels to an acceptable standard," the report concluded. "However, this should not occur in isolation from broader aged care funding reform."
Professor Kathy Eagar, one of the report's lead authors, on Monday gave evidence at the aged care royal commission in Melbourne.
The commission held a minute's silence to honour chairman Richard Tracey, QC, who died on Friday in the US, aged 71.
The inquiry's hearings will go ahead as planned this week, and there will be no delays to the release of the interim report on October 31.