The issue was highlighted in a recent call to the UK-wide MDDUS advice line when a patient had attended a member's practice seeking a referral for elective surgery.
The GP wrote the letter and forwarded medical details to the specialist but disclosed a history of a sensitive and unrelated medical condition, causing the patient to complain.
Dr Gail Gilmartin, a senior medico-legal adviser at the MDDUS, said: 'In providing patient referrals, doctors should include personal information relevant to the medical condition being treated and exercise care in disclosing past history.
'Be aware that inadvertent inclusion of personal details is a greater risk today with most patient information now being held in easily transmissible electronic form.
'Particular attention should be paid to information that the patient is likely to object to having disclosed.'