Professionals attracted to patients should seek advice from a colleague and may have to hand treatment over.The report also warns that obtaining a patient's consent does not justify a sexual relationship.
On its website, the GMC asks doctors and the public whether they agree with the statement "Pursuing a sexual relationship with any former patient will usually be inappropriate".
Consenting adults Two thirds of the 69 people who posted responses said they disagreed with the statement.
Although cases should be judged on an individual basis, the recommendations state that relationships are unprofessional if the patient is exploited, was vulnerable or the professional relationship was terminated to start a sexual relationship.
The report, drawn up by a project team of clinicians, victims of abuse, royal colleges and representatives from healthcare regulatory bodies, also states that all healthcare professionals have a responsibility to report inappropriate behaviour.
It wants to strike a balance between protecting vulnerable patients from abuse and giving doctors autonomy.
Boundaries The GMC's 2001 guidance says doctors must not allow personal relationships to undermine the trust which patients place in them.
Doctors and nurses may be banned from dating former patients unless the contact between them was minimal, according to new draft guidelines.
The recommendations follow a series of high-profile cases where healthcare staff sexually abused patients.
The proposals, the first of their kind, are expected to go before ministers in June, reported Nursing Standard.
The Council for Healthcare Regulatory Excellence said professionals had a duty to report inappropriate behaviour.
"It's always the professional's responsibility to set clear boundaries.