The doctor brother of shadow chancellor George Osborne was found guilty of misconduct yesterday in a case that revealed he wrote a fraudulent prescription for an “escort girl” he was seeing.

Dr Adam Osborne wrote out the form for anti-psychotic drugs on behalf of the cocaine-addicted woman but faked her surname, behaviour ruled to be “dishonest” and “misleading”.

The 33-year-old had earlier admitted to acting in an “inappropriate” manner relating to obtaining the contraceptive pill for his then-girlfriend and an anti-smoking drug for a family member.

The failings were deemed serious enough by a General Medical Council panel to constitute misconduct that impaired his fitness to practice.

He could face being struck off when sanctions are determined later this week.

It was revealed yesterday that Dr Osborne embarked on a relationship with the female escort, referred to throughout the hearing as Miss B, in late 2007 or early 2008.

“The panel was told that your long-term partner was working away from home and you felt isolated,” chair of the panel Alyson Leslie said.