Bullying and harassment at South East Coast Ambulance NHS Foundation Trust has become "normalised", a watchdog says.
The Care Quality Commission (CQC) said its inspection in February followed a high number of whistleblowing concerns raised about the organisation's culture and leadership.
Complaints also included inappropriate sexualised behaviour, the CQC said.
The trust said it was "committed to making improvements".
The leadership at Secamb was rated as "inadequate" by the CQC inspectors.
Amanda Williams, the CQC's director of integrated care, said that "while staff were doing their very best to provide safe care to patients, leaders often appeared out of touch with what was happening on the frontline".
She added: "Some negative aspects of the organisational culture, including bullying and harassment and inappropriate sexualised behaviour, were not addressed and became normalised behaviours.
"There was a clear disconnect between leaders and staff, leading to a poor and unsupportive culture."
Trust 'working to improve'
The CQC is recommending the NHS provides a recovery support programme for the trust - the highest level of support that is offered.
A spokesman for South East Coast Ambulance NHS Foundation Trust (Secamb) says the concerns surrounding culture and leadership "are being taken extremely seriously".
He said Secamb had appointed a new interim chief executive and the trust has already begun work to improve.
Inspectors also looked at the emergency operations centre and the NHS 111 service provided by the trust.
They rated the NHS 111 service as "good" but the emergency operations centre was moved down from a "good" to a "requires improvement" rating.
The CQC has suspended the trust's overall rating until it has completed further checks.