One care worker has been sacked and seven others suspended after secret filming uncovered residents allegedly being taunted, mocked and ignored.
An independent enquiry has been lodged at the Old Deanery care home, on Deanery Hill, Braintree, following footage recorded for the BBC's Panorama programme.
One worker was seen in footage to be slapping a woman.
A statement from care home owner Anglia Retirement Homes said: "As soon as the new management team was made aware of the allegations we took immediate action.
"We hired an independent law firm to carry out a full investigation as a matter of urgency.
"Eight staff were immediately suspended, and have not returned to work, pending a full inquiry.
"Our priority remains the health and wellbeing of our residents and we have more than 200 dedicated members of staff who remain committed to the highest standards of care.
"The care worker responsible for slapping a resident has been summarily dismissed."
Last month, the Braintree and Witham Times revealed staff had been suspended after allegations of mistreatment were made to care home management.
Essex County Council attended a meeting with about 60 relatives of residents after being made aware of safeguarding concerns.
The Panorama edition, Behind Closed Doors: Elderly Care Exposed, was broadcast last night at 9pm.
Full story in today's Braintree and Witham Times