Roger Livermore, an ex-crown prosecutor for the Health and Safety Executive, said prosecutions should have been brought in cases of harm or death.
The Lord Advocate's office said prosecutions were not appropriate.
It said the fact that an incident had occurred did not mean there was "sufficient evidence" of a crime.
Mr Livermore's campaign is supported by Janette and Ian Black, whose daughter Nicola died while being inadequately cared for in a mental health ward.
NHS Ayrshire and Arran was belatedly prosecuted over Nicola's death four years after the incident occurred.
In a letter to Mr Livermore, Gary Aitken, the head of the health and safety division of the Crown Office, said he had looked at 11 incidents but had been advised by the Health and Safety Executive that they  did not fall within its criteria for investigations.
The Crown Office said it had already investigated another 38 incidents raised by Mr Livermore but decided no legal action was required.
"Only in very limited circumstances is the provision of poor quality care or the exercise of poor clinical judgement a criminal matter," he said.
"Such issues may alternatively be dealt with by other regulatory means or by the governing bodies of professional clinicians."
Mr Aitken added: "The fact that an incident has occurred does not mean that here will be sufficient evidence to prove that a crime has been committed."
Mr Livermore is continuing his campaign for a public inquiry into the way the law is being interpreted in Scotland.
In a separate move, the Scottish government has confirmed its intention to introduce legislation to place a legal "duty of candour" on healthcare providers.
The government said it would force health and social care organisations to be open when harm has occurred and provide proper support and training.
It also intends to make the wilful neglect or ill-treatment of patients a criminal offence.
The Crown Office has turned down a request by a health and safety expert to re-open investigations into dozens of incidents at NHS Ayrshire and Arran.