Variation in how coroners report deaths and how police forces decide whether to investigate heavily influence doctors' chances of facing a GNM case, Charlie Massey said.
The GMC chief executive's comments came at a King's Fund and BMJ event on learning from the case of Dr Hadiza Bawa-Garba, who was struck off earlier this year. A medical tribunal ruled that Dr Bawa-Garba should be suspended for 12 months, but the GMC overturned this ruling in the High Court - arguing that a medical tribunal could not take a 'less severe view of the personal culpability' of a doctor than had been established in a criminal court.
Mr Massey told the event on Wednesday: 'Much of the controversy in this case stems from the fact that that we and the tribunal service are obliged by statute to take the outcome of a criminal case as fact.
'What is clear to me is that there is considerable variation in how the law applies across the UK. In England your chances of being prosecuted for GNM hinge very much on how the coroners report death and how police forces then decide how to investigate whatever has come out of that report.
'That’s one of the reasons we have asked Dr Clare Marx to investigate. I am quite convinced that there is considerable variation and considerable scope for improvement.'
Mr Massey told the event that although only nine doctors had been convicted of GNM since 2004, 'the funnel of anxiety and potential prosecution extend much more widely'.
The GMC chief executive said the regulator had not anticipated the scale of the reaction that the Bawa-Garba case would trigger.
'I recognise the issues around confidence in the GMC,' he said. 'We have apologised for the impact on the profession.
He added: 'There is a wider lightning rod point that this case has provoked. A question around the judgment coming at the end of a hard winter, the sense from many doctors that they are working at the limit of their competence, capability, capacity, in hard-pressed health systems with workforce shortages and a lack of resources, and along comes a professional regulator to make many doctors feel that it is just going to take people’s license away when they make an innocent mistake. That is how many people feel.
'The GMC comes at the end of a bit of a conveyor belt – we are not responsible for the criminal justice system, we are not responsible for NHS funding or workforce planning, or indeed working environments and culture, but some of the opportunities for us to grasp do take us into some of that territory.
'One of the most troubling things about this case has been around reflection. Many doctors are very worried. It is fundamental to what we consider as medical professionalism. For our part we have been clear we do not use reflective notes in our processes, we have called for reflective notes to be protected in legal processes. I think that would be highly totemic.'
The GMC chief executive highlighted ongoing work by the regulator to investigate why BME doctors are more likely to face investigation, and pledged to shift the organisation from a point where the bulk of its resources are spent on investigating doctors, to one where the bulk of its resources are spent supporting doctors.