Dr Ubani killed 70-year-old David Gray in February 2008 on his first UK out-of-hours shift by giving him an overdose of diamorphine.
A local government hearing in Arnsberg, Germany, last month is understood to have allowed Dr Ubani to continue to practise medicine.
But in an email to David Gray’s son Rory Gray, local councillor Volker Milk wrote that ‘as far as the doubts from your side about whether or not the doctor has ever sat a state exam are concerned, I can currently only inform you that the investigation into this has not yet been concluded’.
German police records seen by GP show that the state examination office that holds records for the Freidrich-Alexander University in Erlangen Nuremberg where Dr Ubani trained has no record of whether, when or where he sat his medical exams.
A doctors’ chamber in the region where Dr Ubani now practises in Germany hoped to assess him in a fitness-to-practise hearing, but was blocked from doing so after a legal ruling.
In an email seen by GP the Westfalen-Lippe Doctors’ Chambers expresses regret about the decision. A spokesman wrote: ‘The fitness-to-practise interview would have provided the opportunity for Dr Ubani to have dispelled the doubts over his medical qualifications which stem among other things from the events in England. Dr Ubani has missed the chance to dispel our doubts.’
Meanwhile, the GMC recently asked the university examination office to confirm whether Dr Ubani had passed his medical exams, but also drew a blank.
However, the GMC could not obtain the information because it was no longer entitled to after removing Dr Ubani from the UK GMC register.
A spokeswoman at Dr Ubani’s practice in Witten, Germany, told GP he was unavailable for comment.
Rory Gray said the difficulties in proving whether Dr Ubani had passed his medical exams could provide ‘a green light for charlatans and bogus doctors’.
His brother Dr Stuart Gray, a GP in Worcestershire, said: ‘My brother and I deserve to know if our father was killed by someone who’s not a doctor. We are trying our best to get to the bottom of it, but we are hitting huge barriers.’
GMC chief executive Niall Dickson said: ‘We have worked closely with Stuart and Rory Gray to help them get the information they need, including contacting the German authorities.
‘It is important that organisations across Europe work cooperatively and collaboratively to protect patients. We will continue to press for further reforms to ensure this happens.’
A BBC documentary, Killer on Call, will appear on BBC1 East on 10 December at 7.30pm.