GPs must tell the DVLA if a patient continues to drive when they are not medically fit, the General Medical Council (GMC) has said.
In new draft guidance, the GMC said doctors have a public protection duty to inform authorities if a patient is driving against medical advice.
Doctors do not need a patient's consent to inform the DVLA (or DVA in Northern Ireland) when a patient has continued driving.
The strengthened advice is part of a public consultation on the GMC's core guidance on confidentiality.
This aims to help doctors balance their legal and ethical duties of confidentiality with wider public protection responsibilities.
The guidance says doctors must disclose information if there is a need to protect individuals or the wider public from the risks of death or serious harm.
This can include risks of violent crime, serious communicable diseases, or risks posed by patients who are not fit to drive.
Niall Dickson, chief executive of the GMC, said: 'Doctors often find themselves in challenging situations.
"This is difficult territory - most patients will do the sensible thing but the truth is that a few will not and may not have the insight to realise that they are a risk to others behind the wheel of a car.
"A confidential medical service is a public good and trust is an essential part of the doctor-patient relationship.
"But confidentiality is not absolute and doctors can play an important part in keeping the wider public safe if a patient is not safe to drive.
'We are clear that doctors carrying out their duty will not face any sanction - and this new guidance makes clear that we will support those who are faced with these difficult decisions."
Steve Gooding, director of the RAC Foundation, said: "Thirty-seven million drivers depend on the car for getting about and for those with serious medical conditions there is a real fear around losing their licence.
"But with the right treatment, many illnesses will not lead to people having to hang up the keys.
"The worst thing motorists can do is ignore medical advice. If they don't tell the DVLA about something that impacts on their ability to drive safely, then their GP will."
Neil Greig, director of policy and research at the Institute of Advanced Motorists, said: "Clarifying the role of GPs is a very positive road safety move.
"Our research shows that drivers are much more likely to listen to a medical professional giving them advice about giving up driving than to their friends or family."