A scandal-hit ambulance trust is to be put into special measures after a regulator found it was putting patients at risk.
In a series of damning reports, the Care Quality Commission (CQC) detailed how patients had abandoned their telephone calls for help - particularly on weekends - due to problems at South East Coast Ambulance Service NHS Foundation Trust (Secamb).
The regulator also found serious issues with how staff were allocated to ambulances, meaning inexperienced or unqualified staff could be sent to patients, putting them at risk.
It found problems with ambulance handover times to A&E departments, with long delays impacting on the availability of vehicles for other patients. But it found "little sense of urgency" in tackling this issue.
While staff were caring and committed, a recruitment crisis and high staff turnover meant there were not enough people to answer either 999 calls or calls to the NHS 111 service run by Secamb, the CQC reports said.
Secamb is the worst performing trust nationally for answering 999 calls within five seconds, and is failing to achieve national performance targets for the highest priority calls.
The trust, which provides services to Kent, Medway, Surrey and Sussex, has repeatedly come under fire in recent months over its high-risk scheme - now abandoned - to delay ambulances to patients.
Under the controversial plan, the trust gave itself up to 10 extra minutes to reassess what type of advice or treatment some patients needed, and whether an ambulance was really necessary.
In the new reports, the CQC ranked Secamb as inadequate. It said its emergency and urgent care services were inadequate and that the emergency operations centre and 111 service require improvement.
The CQC found allegations of bullying and harassment of staff and said staff morale was generally low.
It said: "We heard that staff were tired and exhausted. Paramedics told us they felt burnt out."
On 111, the regulator said: "The number of staff available was often below those identified as being needed to manage patients' calls and this often led to long delays in calls being answered and calls being abandoned by patients, placing them at risk."
Other damning findings unveiled by the CQC reports included:
:: Outcomes for Secamb patients who had a cardiac arrest were "worse than the national average", although stroke care was good.
:: Medical equipment on ambulances could not be shown to be adequately maintained or safe to use.
:: The processes for reporting and investigating incidents and the lack of learning from incidents "did not support the safe provision of service".
:: Safeguarding arrangements within the trust were "exceptionally weak". A lack of accountability and investigation was "prevalent throughout the trust".
:: There was little evidence of learning from complaints across the whole trust.
:: There was poor practice over infection control.
:: Patient records were not always completed fully or appropriately.
:: Some 3.1% of 111 calls were abandoned by patients, compared to the England average of 2.4%. At weekends, this could run as high as 44% of calls abandoned by patients. The CQC said a "high call abandoned rate is considered not to be safe and may reflect a high level of clinical risk for patients". Overall, it said there were "not enough staff to keep patients safe".
Professor Sir Mike Richards, NHS England's Chief Inspector of Hospitals, said the trust had gone through significant upheaval due to changes in its management and praised the dedication of staff.
He added: "While we have significant concerns about the performance of the ambulance service, I want to provide some reassurance.
"Once care arrives, it is of a good standard - with dedicated and caring call handlers, ambulance crew, paramedics and other frontline staff working hard to ensure this.
"Secondly, the trust are taking urgent steps needed and some improvements have already been made - to ensure that everyone who relies on this service receives excellent, timely care."
NHS Improvement said it would soon appoint an improvement director at the trust and would place it in special measures on recommendation from the CQC.
Anne Eden, executive regional managing director for the South at NHS Improvement, said: "We know that more people than ever are requiring urgent or emergency care this year and that the demand is challenging trusts across England.
"However, the serious concerns about care at South East Coast Ambulance Service need to be addressed quickly, which is why we are putting the trust in special measures."
Secamb's acting chief executive, Geraint Davies, said 60 new frontline staff had joined the trust since April and that it had developed a plan on areas including recruitment, retention and performance.
He conceded that it was a "challenging time" for the trust and that "serious concerns" needed to be addressed.
He said: "We understand the seriousness of placement into special measures but would value the additional support that this would offer us.
"We expect that the move will mean the work we have already started can continue at pace."
He went on: "Following initial feedback from the CQC we have already been working on and implementing a number of improvements."