The Commissioner for older people, Eddie Lynch has said he can give no assurances that residents at a Londonderry care home are safe.
Owen Mor caters for people with learning disabilities and dementia.
The facility remains under enforcement after the health regulator, the RQIA, raised safety concerns in August.
An investigation in May found patients missing medicines, nurses not following procedures and inadequate record keeping.
In an unprecedented move, the RQIA obtained a court order in August to stop new admissions after it emerged the Western Trust was still referring patients to the home.
Asked by the BBC Radio Ulster's Nolan Show if he could make any guarantees over current residents' safety, Mr Lynch said he could not make any assurances people in the nursing home are safe under the current standards.
"I don't believe you can make that statement as long as the home remains in failure to comply with the minimum standards," Mr Lynch said.
"How you can say you can be assured that people are safe?
"It is an unbelievable situation that six months on that this is the case", he said.
Dr Bob Brown, the director of care and older people's services at the Western Health Trust, told BBC Radio Foyle on Thursday: "It is not possible for me to give assurance that every resident is receiving safe and quality care at every moment in time."
He met with councillors at a health and communities committee meeting at the Guildhall on Thursday to address concerns over the 81-bed facility.
Relatives of Owen Mor residents were in the public gallery and applauded as councillors from Derry and Strabane District Council raised their fears with the Western Trust.
'Number of incidents'
One of those councillors, Raymond Barr, had his daughter admitted to the Culmore Road home last year for three weeks.
Four years ago the independent councillor's daughter suffered a diabetic coma which left her blind and disabled.
He said he was shocked by a number of incidents during that time and said there had been a failure to give his diabetic daughter her insulin.
Asked about the current status of the Owen Mor facility, Dr Brown said: "It takes time to achieve sustainable improvement."
In May, inspectors highlighted failings around patients missing medicines, nurses not following procedures and inadequate record keeping around falls, feeding and nutrition.
Calls for closure
Aidan Hanna of patient advocacy group NI Patient Voice believes the care home should be closed unless serious changes are made.
"Under the current ownership I don't believe it should be open," he said.
Dr Una McDonald, a spokesperson for Owen Mor, said regulators had noted improvements at the care home in their most recent inspections.
"Owen Mor absolutely has a future and, in my opinion, will not be shut down.
"Very few people want to see Owen Mor shut down, it's not my intention, it's not the directors' intention and it doesn't appear to be the intention of the Western Trust or the RQIA unless we were to revert and progress didn't continue as it has been."
A spokesperson for Owen Mor management said they have been "working closely with its regulator the RQIA and the Western Trust to move to full compliance and have the current enforcement notice lifted".
A spokesperson for the regulatory body the RQIA said: "Owen Mor remains under enforcement action.
"During our most recent inspection in late October, we were pleased to find significant progress towards addressing the concerns identified by RQIA.
"The safety and wellbeing of everyone living at Owen Mor is of utmost importance," the spokesperson said.