Britain’s first post-operative transgender doctor is under investigation following complaints that he provided inappropriate treatment to patients wishing to change gender.

Dr Richard Curtis is being investigated by the General Medical Council (GMC), after at least three separate complaints.

The London-based GP is accused of prescribing hormone therapy to several patients – when it was not suitable to do so – and also ignoring restrictions placed on his practice.

The Telegraph states in one case reportedly under investigation by the GMC a woman complained she regretted undergoing treatment, which included having a double mastectomy and taking hormones.

In another case, it was alleged Dr Curtis prescribed drugs to patients under 18, without the specialist knowledge or the skills to do so.

Dr Curtis is also accused of failing to follow acceptable levels of care and breached conditions placed on his practice by the Medical Practitioners Tribunal Service (MPTS), the GMC’s arm’s-length disciplinary body.

Dr Curtis, who is believed to live in Richmond, south-west London, qualified in 1991 from St Bartholomew’s Medical College and became a GP in 1995.

He took over the London Gender Clinic five years ago and according to his website boasts “substantial expertise in helping people with gender dysphoria seeking to undergo gender reassignment achieve the best outcome throughout the course of their journey”.

Dr Curtis underwent gender confirmation surgery in 2005.

A spokesman for the Medical Defence Union, which is representing Dr Curtis, said he was unable to comment on any of the allegations “because of the ongoing investigation and his duty of patient confidentiality”.

A GMC spokesman was unavailable for comment.