Ten workers at a mental health unit have been suspended amid claims patients were "dragged, slapped and kicked".
Inspectors said CCTV footage recorded at the Yew Trees hospital in Kirby-le-Soken, Essex, appeared to show episodes of "physical and emotional abuse".
The details emerged in a Care Quality Commission (CQC) report after the unit was inspected in July and August.
A spokeswoman for the care provider said footage had been passed to police.
The unannounced inspections were prompted by managers at Cygnet Health Care, who monitored CCTV footage of an incident on 18 July.
At the time, the 10-bed hospital held eight adult female patients with autism or learning disabilities.
'Abusive, disrespectful behaviour'
The CQC reviewed 21 separate pieces of footage, concluding that 40% "included examples of inappropriate staff behaviour".
"People who lived there were subjected not only to poor care, but to abuse," a CQC spokesman said.
Workers were captured "physically and emotionally abusing a patient", and failing to use "appropriate restraint techniques", the report said.
It identified "negative interactions where staff visibly became angry with patients" and two cases where staff "dragged patients across the floor".
"We witnessed abusive, disrespectful, intimidating, aggressive and inappropriate behaviour," the inspectors said.
Suspended workers "included people we believe witnessed the alleged incidents and failed to report them," a spokeswoman said.
Dr Kevin Cleary, the CQC's mental health lead, said the failure of some staff to raise the alarm "perpetuated abuse and allowed a culture of poor care to become established".
"Cygnet's leadership made efforts to address the harm people experienced while in its care, including suspending staff and making police referrals," he said.
"This does not change or excuse the fact that a culture was allowed to develop at this hospital which led to people suffering abuse."
He added: "Any enforcement action we may take will be published as soon as legal restrictions allow."
Another Cygnet hospital, Thors Park in Brightlingsea, closed in June 2020 after it was rated inadequate by inspectors.
A CQC report revealed that "patients and others were placed at risk of harm".
Hospital managers were investigating 27 members of staff, it said, and found "poor employment screening" among clinical support workers.
A spokeswoman for Cygnet Health Care told the BBC: "Cygnet has a zero-tolerance approach to any kind of abuse, which is why the well-established policies and processes we have in place to safeguard people in our care were backed up by the use of closed-circuit TV at Yew Trees.
"The safety and wellbeing of the people in our care is our absolute priority, and we are appalled by the actions of this small minority.
"We are also doing everything we can to assist the authorities to fully investigate what happened."
Two members of staff had been referred to police, she added.
Essex Police has been approached for comment.