A new report commissioned by Age Action has highlighted fears of a repeat of the Leas Cross scandal.
The study found standards here lag far behind other developed countries with the cost of care €400 a week below what it should be, and it warned the financial shortfall was being met through a drop in care.
Report author Brian McEnery said a repeat of the Leas Cross controversy would only be avoided through extra cash from the Exchequer.
"Unless there are mandatory staffing levels and unless the operator is reimbursed for employing this staffing level, then there will continue to be stories like Leas Cross Nursing Home," he warned.
Patients in Leas Cross were subjected to systematic and institutional abuse, and the consultant geriatrician Prof Des O'Neill, who examined the home before its closure in August 2005, warned it could be repeated elsewhere.
The Age Action report analysed accounts and staffing in 16 private nursing homes and two public nursing homes.
It said for private homes to provide care in line with good international practice it would cost €1,101 per resident per week in urban areas and €994 in rural areas. But the study found the average private nursing home in Ireland last year charged €694.20 per week.
Mr McEnery said the shortfall in costs was accounted for by a shortfall in care.
Age Action chief executive Robin Webster said the report was important in establishing the cost of proper care. "But the underlying message is that we must ensure we have quality of care," he said.
"If you are going to pay €1,000 a week to a nursing home you want a real assurance that the quality of care you receive matches international standards."
The study found in Ireland, the average number of care hours per resident per day last year was slightly over 2.4 for private nursing homes - 1.46 hours short of the UK recommendation.
In public nursing homes, the average number of care hours per resident was 2.91 hours per day in the rural home - 0.95 hours short of the UK recommendations.
However in public homes in urban areas it was 3.87 hours — exceeding UK standards.
Tadhg Daly, chief executive of the Irish Nursing Homes Organisation, said the HSE had questions to answer over the the differences in fees between public and private homes.