Labour has called for a national whistleblowing hotline for NHS staff after data from health boards revealed only one instance of it in the last two years.
The party contacted all NHS boards asking if they had recorded instances of whistleblowing, with only NHS Greater Glasgow and Clyde stating it had dealt with a case.
An independent report on NHS Lothian, published earlier in May, found that bullying was common at certain levels within the organisation.
The study was ordered after concerns about the board's culture were raised during an investigation into the manipulation of waiting times.
The report said NHS Lothian's management style was "creating an undermining, intimidating, demeaning, threatening and hostile working environment for some staff" as well as a reluctance to pass bad news too far up the management chain.
Labour is due to hold a debate on waiting lists and NHS management culture in Holyrood on Thursday.
Dr Richard Simpson, the party's health spokesman, said: "Our NHS does a great job, but for there to be only one report of whistleblowing in our entire NHS in the last two years is deeply worrying."
He said: "At NHS Lothian, staff felt too scared to speak up for fear of reprisal. That is not right.
"These figures suggest that culture could extend beyond NHS Lothian.
"Frontline NHS staff know better than anyone else the issues facing our NHS and often spot problems first. They must feel safe in the knowledge that if they flag up genuine concerns they will not face reprisal."
Dr Simpson said a national hotline would allow concerns to be properly dealt with when they were raised and a register of complaints would mean senior managers would be aware of problems in hospitals.
A Scottish Government spokeswoman said: "While inappropriate management styles were found to be originating from the top level at NHS Lothian - the report makes clear that there is no general condemnation of management and there is no suggestion of this issue in other boards.
"There is absolutely no place for bullying in the NHS and it will not be tolerated.
"Across NHS Scotland much has been done to tackle bullying and harassment in the workplace and to promote the standards of behaviour that is acceptable and expected in each organisation."