An NHS Trust, which was heavily criticised for "a string of failings" when a vulnerable 18-year-old drowned in a bath while in its care, has been told it needs to make 'urgent and significant' improvements.
The Care Quality Commission (CQC) has told Southern Health NHS Foundation Trust that it had failed to learn from previous mistakes.
In October, a jury inquest ruled that neglect contributed to the death of Connor Sparrowhawk, who drowned after an epileptic seizure at Slade House in Headington, Oxfordshire, in 2013.
The learning disability unit, run by Southern, has since shut down.
CQC inspectors visited the Trust in January as part of an inspection and found "long-standing risks to patients."
The CQC said it has now issued a warning notice "requiring the trust to improve its governance arrangements to ensure robust investigation and learning from incidents and deaths, to reduce future risks to patients".
The CQC will publish its full report in late April.
NHS Improvement said it intends to take further regulatory action at the trust to ensure urgent patient safety improvements are made.
Katrina Percy, chief executive of Southern Health, admitted "we have a lot of work to do to fully address recent concerns raised about the trust".
Luciana Berger, Labour's shadow minister for mental health, said she would raise the issue when Parliament resumes next week, adding: "It is extremely worrying that the trust's leadership has not taken the appropriate action to improve patient safety."