GPs have been advised to familiarise themselves with the General Medical Council's (GMC) updated guidance on confidentiality, which comes into effect on 12 October.
The Medical Defence Union (MDU) says nearly a fifth of calls the medical defence organisation receives concern confidentiality and disclosure of information – around 4,000 calls a year.
Dilemmas raised by MDU members include whether to reveal a patient's name and address to the police who had found a practice appointment card at the scene of a crime and whether to disclose information to the DVLA about a patient who refuses to stop driving a lorry even though he has suffered a blackout.
Dr John Holden, MDU medicolegal adviser, said: "Confidentiality is central to the relationship of trust between patients and doctors. Without assurances about confidentiality, patients may be reluctant to give doctors the information they need in order to provide good care.
"However, it is well accepted that a breach of confidentiality can sometimes be justified, legally and ethically, in the public interest. For example, when failure to do so may expose the patient or others to risk of death or serious harm.
"Decisions about whether to disclose confidential information are one of the key reasons members seek our advice, and the GMC's guidance, as well as providing helpful advice, ultimately establishes how doctors will be judged in the event of a GMC complaint."
The GMC has also issued new supplementary guidance to accompany the core guidance on confidentiality, which it plans to review regularly. This includes guidance on responding to criticism in the press.