The Care Inspectorate has raised serious concerns about the poor quality of care at Pentland Hill nursing home in Edinburgh following a significant number of complaints in the last year.
Police are also investigating the death of a 67-year-old resident at the Bupa-run care home last month.
The inspectorate carried out an unannounced review in July after upholding three complaints from families of residents in the past year.
Inspectors found problems with the quality of care and with the management of the home in Gylemuir Road.
It has issued a formal improvement notice and new admissions have been suspended until improvements are made.
A Care Inspectorate spokesman said: "We have serious concerns about the quality of care and management in this home and have issued a formal improvement notice. This requires urgent changes to be made to bring the home up to scratch, and we are working closely with the provider to make that happen.
"Everyone using a care home has the right to care that reflects their needs and promotes their rights and if that does not happen, we will not hesitate to take enforcement action.
"New residents should not be admitted to this home until improvements are made, and the provider has voluntarily agreed to this.
"We continue to liaise with the local authority and the police about some specific incidents."
A police spokesman said: "Police are carrying out inquiries into the death of the 67-year-old resident at Pentland Hill care home last month."
An investigation is standard procedure in deaths of this type, he said.
Bupa Care Homes area director for Scotland Kirsty Dace said: "The health and well-being of our residents is our absolute priority and we are working closely with the local authority and the Care Inspectorate to address the issues raised.
"We are meeting with our residents, relatives and staff to keep them fully informed of progress of our action plan."