Eight care workers at an Essex care home have been suspended after secret cameras filmed alleged poor care of residents.
Anglia Retirement Homes said it had launched an independent inquiry into the allegations after the BBC says it filmed staff mocking residents and ignoring their calls for help.
One care worker who was caught slapping a women was "summarily dismissed", it added.
The alleged mistreatment at the Old Deanery in Essex, a 93-bed home in Braintree, was filmed last year by an undercover reporter for the BBC.
Anglia Retirement Homes told the BBC the incidents involved a "small number of staff" and were not reflective of the high standards of care it demanded.
A statement 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."
It added: "The care worker responsible for slapping a resident has been summarily dismissed."
Concerns were first raised about the home by whistle-blowers in 2012.
In its latest inspection in February the Care Quality Commission (CQC) reported the home had too few staff and some residents waited too long for staff to answer their calls.
The company was taken over by new owners last November.
Further footage filmed in 2012 by the relative of a resident at a separate care home in Croydon, south London, will also be broadcast tonight as part of the BBC Panorama documentary looking at elderly care standards.
it shows staff repeatedly neglecting 98-year-old Yvonne Grant who has since died. Her calls were ignored hundreds of times by staff at Oban House, run by HC-One, the UK's third biggest care home provider.
Grandaughter Vanessa Evans, who hid the cameras on three days, told The Daily Mirror she was "devastated and fuming" but not shocked.
"I was expecting to find something but I didn't think it would be this extreme," she said.
A HC-One spokeswoman said the poor care "was not, and is not, indicative of the standards we demand and was contrary to all of the processes and training we have put in place".
She said: "We apologise unreservedly for those failings in 2012."
The care home provider is now considering whether to install visible CCTV cameras in all of its care and nursing homes, she added.
HC-One was formed in 2011 following the collapse of the UK's then largest nursing home operator, Southern Cross Healthcare.
The BBC reported that figures from the CQC show over a third of homes which received warning notices in 2011 still do not meet basic standards.
Andrea Sutcliffe, chief inspector of social care at the CQC, told the BBC: "There are organisations who are running care homes, they're getting paid to provide care and to provide support.
"And they need to be making sure that they're meeting the needs of the people who are using those services, they're making money out of these services. People shouldn't be getting into this business if they don't care."
:: BBC Panorama's Behind Closed Doors: Elderly Care Exposed will be broadcast on BBC1 at 9pm today.