Inspectors have issued Derriford Hospital bosses with a warning to make significant and immediate improvements to its emergency department after the safety of the service was found to be "inadequate".
During a visit in March, the Care Quality Commission (CQC) found patients were put at risk by long waiting times and ambulances were also being held for too long, meaning they could not respond to other calls.
Inspectors found the service did not have enough medical staff to meet the recommended guidance and patients with mental health needs were not always seen in a timely manner or cared for in an appropriate environment.
Following the inspection, the CQC issued University Hospitals Plymouth NHS Trust - which runs the hospital - issued a warning notice outlining the areas for improvement in the department, including two breaches of legal requirements which must be put right.
When publishing the results of the inspection on Wednesday 19 May, the CQC said inspectors looked only at how safe, responsive and well-led the urgent and emergency care department was during the focused inspection.
Inspectors found there had been a deterioration in the quality of services being provided and so the safety of the service - which was previously rated as 'requires improvement' - is now rated as 'inadequate'.
Where it used to be 'good' for being well-led, it is now rated as 'requires improvement'.
How responsive it is was not rated so the previous rating of 'requires improvement' remains.
The overall rating for the urgent and emergency care service at Derriford Hospital remains 'requires improvement'.
During its visit, the CQC also looked at the diagnostic and imaging services in response to concerns about the safety and quality of the service. Its overall rating did not change and remains 'requires improvement'.
The overall rating for both University Hospitals Plymouth NHS Trust and Derriford Hospital also remains unchanged and is 'requires improvement' in both cases.
CQC’s head of hospital inspection for the south, Amanda Williams, said: "When we inspected Derriford Hospital’s urgent and emergency care department, we found that people were waiting too long to be seen.
"This meant that there was a risk to patients who were unable to access care and treatment in a timely way. There was also a further risk, because ambulances were being held for too long in the system, which meant they were unable to respond to calls from other patients who needed urgent assistance.
"We also inspected the diagnostic imaging service and I am pleased to report that governance processes are now operating effectively and the service is being well run. Staff felt respected, supported and valued and they felt that the leaders were proactive with their support."
In response to the CQC's findings chief executive at the trust Ann James said she is "delighted" to see inspectors recognised improvements made in diagnostic imaging but "disappointed" to receive the warning notice for the emergency department service.
She said staff have worked hard during the global pandemic and said it's good inspectors recognised staff were "focused on the needs of patients receiving care".
She added: "We have provided the CQC with evidence of the immediate actions we have already taken to address their concerns and ensure patients attending the department are safely cared for."
She said the trust is "committed" to making improvements, adding: "We have a good record of being able to turn things around. We also have a bright future to look forward to with plans for a new Urgent and Emergency Care Centre."