The NHS trust that runs Brighton's main hospital has been downgraded after whistleblowers prompted an inspection.
The Care Quality Commission (CQC) found standards at two hospitals run by University Hospitals Sussex NHS Foundation Trust had fallen. Urea System Assembly
Inspectors said staff and patients were being let down by senior leaders who "often appeared out of touch" with what was happening in clinical areas.
The trust's chief executive said it was committed to addressing the issues.
The CQC called for rapid and widespread improvement, adding it would not hesitate to take action to keep people safe.
It has recommended to NHS England the trust receives the highest level of support. NHS England told the BBC it would continue to support the trust and would consider the CQC's further recommendation.
Deanna Westwood, CQC director of operations in the South, said inspectors found frontline staff "doing their best" to provide safe and effective care and treatment, despite significant pressures.
But she said: "Staff and people using services were being let down by senior leaders, especially the board, who often appeared out of touch with what was happening on the wards and clinical areas."
She said staff felt unable to raise concerns without fear of reprisal, adding: "I want to praise those who were brave enough to come forward anyway, despite those fears. Speaking up in these circumstances isn't easy but is incredibly important."
Inspectors found a culture development where safety concerns were normalised and a disconnect between leaders and staff.
In neurosurgery, the service did not have enough staff, availability of equipment did not always support safe and effective care, staff did not feel supported and did not always work well together.
Across the trust, staff felt bullying was unaddressed, there was little point in raising concerns, they felt pressured into making unsafe decisions and minority ethnic staff were more likely to experience poorer outcomes.
Overall, the trust was downgraded from outstanding to requires improvement.
Brighton's Royal Sussex County Hospital fell from good to inadequate and the Princess Royal Hospital, Haywards Heath, dropped from good to requires improvement.
Trust chief executive Dr George Findlay said: "When I took up this role just under a year ago, I commissioned an external review to give me a clear picture of where we stood as a newly formed trust, our strengths and our weaknesses.
"Everything the CQC is saying now chimes with what we already knew, and had committed to addressing right from the start.
"I'm extremely proud of the huge strides colleagues have made, but we all recognise how much work still lies ahead. The seven months since this inspection have seen rapid progress, now we need to push on again."
In an interview with BBC Sussex, Dr Findlay said people using hospitals could be assured they were safe, adding: "Our staff are amazing and they do a great job every day."
He said: "It's important to remember that while there are lots of negatives in this report there are real positives.
"The CQC itself said most patients praised the care and treatment and support they received. Care is outstanding. Effectiveness remains outstanding."
The trust's hospitals also include Southlands Hospital, St Richard's Hospital, Worthing Hospital and Hove Polyclinic.
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