Doctors are fearful of being victimised by their bosses and damaging their career prospects if they raise concerns about patient care or staff behaviour, medical chiefs claim.
Worries about patient care or staff behaviour are not reported by 40% of doctors, a survey by the British Medical Association (BMA) found.
More protection must be given to protect NHS doctors from being victimised by their bosses, the BMA said.
Dr Charles Saunders, chairman of the BMA's Scottish Consultants Committee, said: "As clinical leaders, doctors have a duty to speak out when they have concerns. However, as the results of this survey bear out, this is not always possible or effective.
"We have concerns around the culture of many NHS organisations. Doctors tell us they fear their careers can be affected by speaking out – this is completely wrong.
"We must move to a culture where every individual in a health organisation can raise concerns that are looked at and acted upon appropriately."
Almost 80% of the 384 doctors who took part in the survey, entitled Standing up For Doctors; Speaking Out For Patients, were not aware of the whistleblowing policy for employees at the NHS board where they worked.
Around six in every 10 doctors said they had experienced occasions when they have had important concerns about working practices or the behaviour of staff – but only 60% of them reported it.
Those who did not believed that either reporting their worries would make no difference or that they feared the consequences of doing so.
One in 10 doctors who did raise concerns said they were given indications that speaking out could have a negative impact on their employment.
Almost half of concerns, 44%, regarded standards of care, and 37% were about the behaviour of fellow staff. Around one in five cases related to targets or strategies of NHS boards.
"A culture-change needs to come from the very top," Dr Saunders said.
"Ministers and NHS board members need to send a clear message that they want to hear about things they can do better."
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