Inspectors discovered numerous problems, including a resident who spent two months sleeping in an armchair, and put a care provider under special measures.
In the city's Greenwich Gardens, Parkland View, and Cedar House, CRT-Derby Extra Cares offers personal care to residents who live in their own apartments.
The Care Quality Commission (CQC) has now assigned it an "inadequate" rating.
The company has six months to "significantly improve".
With a variety of needs, including autism, learning and physical disabilities, mental health support, and dementia patients, CRT provides services for 122 residents in three assisted living settings.
A resident had reportedly been sleeping in a chair for the past two months, according to the report that was published.
Inspectors were informed by a staff member that they had expressed their concerns to managers, "who had not acted," and that they believed the employee was being neglected.
The staff "did not always use facemasks" when supporting residents, according to residents, and PPE and continence aids were "not always safely disposed of and left in their flats.".
According to inspectors, staff "did not always stay for the full duration of scheduled care calls.".
Additionally, a family member complained that "staff sometimes miss visits because they're so busy," and another told the CQC that they were worried about someone who was "not receiving support to change into clean clothes.".
Inspectors also discovered that 33 staff members who had been working there since September 2021 hadn't finished the necessary training and that medication wasn't always administered on time.
The care was "excellent," according to a resident who spoke with inspectors.
According to the CQC, "This service's overall rating is inadequate, and as a result, special measures have been taken.".
This indicates that we will continue to evaluate the service, and if we do not propose to cancel the provider's registration, we will re-inspect after six months to look for appreciable advancements. ".
CRT has been reached by the BBC for comment.
