A health watchdog is investigating allegations by whistleblowers that Cornwall's out-of-hours GP service is "unsafe" and manipulated results to avoid missing targets.
Private health company Serco, which runs the service, was probed by health regulator the Care Quality Commission in an unannounced inspection last month.
The company has fiercely defended its reputation insisting the service is safe and well run, with patients reporting a high level of satisfaction.
But according to allegations made in the Guardian newspaper, Serco allowed queues of up to 90 patients at a time to build up on a telephone helpline, met targets in part by adjusting figures to blame delays on patients and took visiting doctors off roving duty to operate clinics and hotlines because it was short-staffed.
Critics of the service said they have been pressured to keep quiet and say Serco has launched an investigation of email traffic to see who has leaked information. Serco said any monitoring of emails was within the law and was to protect patient confidentiality.
Dr Gareth Emrys-Jones, a retired BMA council member and former chairman of the GP co-operative that used to run the out-of-hours service for Cornwall as a not-for-profit company, was one of several people who contacted the CQC.
He said: "I have been approached by a significant number of people representing all classes of employees at Serco who felt unable to whistleblow directly but who perceived the service to be unsafe because of a lack of clinicians and inadequate cover for the needs of the patients of Cornwall."
Staff allege that shifts for doctors and nurses have repeatedly been unfilled in the past few months, so that target times for visiting the sickest patients at home have been missed. Shortages in the call centre where patients are first assessed have resulted in long queues building up and clinicians have been pressed to downgrade the priority of calls because there are not enough doctors available to make home visits, according to claims.
A spokesman for the CQC said its report into Serco would be out "in due course".
A Serco spokesman said: "A substantial number of the allegations have been raised before, fully investigated by a number of independent bodies and found to be false and without foundation."