Some district health boards fear serious problems in rest homes could be missed if the Ministry of Health becomes solely responsible for auditing facilities.
The ministry will shortly take over routine auditing of aged care facilities under a national agreement with health boards.
Until now, each health board has carried out its own contract audits, while the ministry has done separate certification audits.
MidCentral District Health Board says it has serious concerns about the Ministry's auditing process after its own inquiry found serious safety concerns at eight certified rest homes, ranging from medication errors to poor clinical oversight.
One home had passed a Health Ministry certification audit on the same day MidCentral's auditors found major risks to residents, the board's review said.
However a District Health Boards New Zealand spokesperson, Chris Fleming, says boards will still be able to investigate complaints.
Most boards are working together to get the best outcome, and to reduce the duplication that had been part of the old system, he says.
Aged Care Association chief executive Martin Taylor says the vast majority of the 42,000 people in homes nationwide receive excellent care.
Mr Taylor says any health facility can be called into question on any number of things during an audit.
"For example I'm sure if MidCentral was audited as much as the aged care sector, you'll be able to find issues, as confirmed by the number of their sentinel and serious events."
Mr Taylor says MidCentral DHB is trying to use the report to fight the revamp of the audit regime.
Green Party health spokesperson Sue Kedgley says problems of staff shortages, lack of training, high turnover and poor pay are endemic in the aged care sector.
"All the auditing in the world isn't going to help if we have a sector where you're chronically short of staff.
"You cannot get decent care when you've got one person looking after up to 30 residents - it's just not possible."
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