The Care Quality Commission (CQC) has published a report criticising out-of-hours GP services in Cornwall and the Isles of Scilly.
Serco Ltd, who provide the services, have been warned that they must take action to improve, after failing to meet four of the essential standards on quality and safety.
During inspections conducted in April and May, it was observed that people who use the service were not safeguarded from abuse due to a lack off suitable staff training.
Inspectors also noted that staff and training issues meant there was a shortage of clinical staff, leading to long GP shifts and increased waiting times. A quarter of staff had not completed mandatory training.
On one occasion, doctors were observed working shifts of up to 13 hours.
During the inspection period, one patient was forced to wait at a clinic for 90 minutes, whilst another was left waiting so long for a home visit that they dialled 999.
Serco admitted that they had underestimated the demand over the Easter weekend and May Bank Holiday period, leading to delays.
The inspection also highlighted the lack of an efficient quality assessment and management system within the service.
Daily performance reports recording whether the service was meeting its targets were routinely altered by managers if they were felt to be incorrect. However, the company admitted that entries that may have been recorded incorrectly in their favour were not routinely amended. Inspectors did not feel however that there was any deliberate attempt to enhance figures.
Despite a whistleblowing procedure being in place, staff claimed that they would not feel comfortable raising concerns with management.
Ian Biggs, deputy director of CQC in the South said:
"At least half a million people depend on this service, so it is vital that it is properly staffed with properly qualified GPs who are available when people need them.
"At times, Serco has not had enough doctors on duty and it is hardly surprising that people have complained. Asking GPs and their drivers to work such long hours should be a last resort."
The provider has been given 14 days to supply a report describing how it will achieve compliance.