A leading expert in transsexualism is being investigated by the General Medical Council.
The GMC is investigating the complaint
It is alleged that Dr Russell Reid gave patients hormone treatment or referrals for surgery without adequately assessing them.
A complaint detailing 12 patients treated by Dr Reid has been submitted to the GMC by three other experts in gender identity disorder.
It is alleged some patients regretted changing sex.
The GMC confirmed that Dr Reid, a member of the Royal College of Psychiatry's committee on gender identity disorder (GID), is under investigation.
He is set to appear before the GMC's interim orders committee, which could suspend him or restrict his work, on Tuesday.
The complaint centres around the interpretation of guidelines on the treatment of GID set by the Harry Benjamin International Gender Dysphoria Association, based in Minneapolis.
The guidelines, which are supported by the Royal College, suggest "flexible directions" for the treatment of GID.
The psychiatrists say Dr Reid has not adhered to the requirement for patients to have been living in their desired gender role for at least three months, or have had three months of psychotherapy before they are prescribed hormones.
The guidelines also suggest patients should live as their desired gender and have hormone treatment for at least a year before they are referred for surgery.
But they say patients can be given drugs earlier if it is feared they would otherwise obtain medication on the black market or resort to unsupervised use.
A spokesman for the Medical Defence Union, which is representing Dr Reid, said he did not want to comment on the investigation at this stage.