The Care Quality Commission has issued a formal warning to Avon and Wiltshire Mental Health Partnership over levels of staffing at Blackberry Hill Hospital in Bristol.
It followed an unannounced inspection of three wards at the Fromeside Unit in December. The medium secure unit provides specialist care and treatment for adults with mental disorders, which may mean that they are at significant risk of harming themselves or others.
Inspectors found that the unit was failing to comply with the national regulation on staffing and did not have not enough qualified, skilled or experienced staff to meet people's needs.
More top news
'In Avon and Somerset we stand shoulder to shoulder with colleagues in the Metropolitan Police Service and the communities we serve.'
MPs from across the region have been reacting to the terrible events that unfolded in Westminster yesterday.
The man who carried out the Westminster attack is thought to be British born and was once investigated by MI5, the Prime Minister has said.