A mental health unit for young people where two patients died in two months has been rated inadequate.
The Care Quality Commission (CQC) found patients at West Lane hospital in Middlesbrough were not safe and at high risk of “avoidable harm”.
Inspectors found not all staff had the skills or experience to do their job, and some wards had insufficient staff.
The Tees, Esk and Wear Valleys NHS Trust said it was taking “urgent action” to address the issues raised.
Admissions to the hospital were temporarily suspended following the death of 17-year-old Christie Harnett in June, and on 9 August Nadia Sharif, also 17, died.
Both their families have called for action to be taken to prevent further deaths.
In March it was revealed 13 members of staff were facing disciplinary proceedings over the alleged ill treatment of patients.
The CQC inspection, carried out over three days in June, uncovered a catalogue of failings, including “substantial and frequent staff shortages” and that staff did not always “adequately assess, monitor or manage risks to patients”.
Non-approved restraint techniques had been used, people were at risk because staff did not store medicines safely, and there were out-of-date medicines still in use.
In addition, staff did not feel supported or valued, with morale low, and some told inspectors not all incidents were reported.
The trust said there was a national shortage of the specialist staff to properly support the “complex needs of young people in mental health inpatient wards”.
In July it had consolidated the number of wards from three to two, in a bid to address the staffing problem, allow more time for training, and improve safety, it said.
There was also “ongoing work to reduce the use of restrictive interventions”.
Elizabeth Moody, the trust’s deputy chief executive, added: “Our patients are always our priority… we are committed to making the improvements necessary.
“We will continue to work closely with the CQC, staff, and most importantly the young people in our care and their families, to ensure we provide better care at West Lane Hospital.”