Nurses, midwives, porters and cleaners were surveyed
One in three NHS workers who has voiced concerns about bad practice in the service has faced reprisals, figures reveal.
Unison says health workers are most afraid of raising concerns about bullying, staffing levels, meeting government targets and waiting lists.
And one out of every three of the 2,000 nurses, midwives, porters and cleaners asked said their NHS trust would not welcome reports of a major problem.
The public services union is calling on employers to impose clear policies to protect workers and promote "open and easily accessible" ways of raising concerns.
It is essential for staff to be able to raise concerns about standards of
patient care or staff safety without the fear of reprisals
Unison head of health Karen Jennings
Unison head of health Karen Jennings said it was very worrying that one out of every two workers surveyed did not even know if their
health trust had a policy on "whistle-blowing".
And it was appalling trusts were "failing in their duty of care to
patients and staff by burying their heads in the sand".
"It is essential for staff to be able to raise concerns about standards of
patient care or staff safety without the fear of reprisals," she said.
Ms Jennings said employers must have
clear whistle-blowing policies open and easily accessible to everyone
"It is very worrying that half of all those asked did not even know if their
Trust had a whistle-blowing policy," she said.
Unison's report said there was a "reality gap" between government initiatives to
promote whistle-blowing, and what was happening on the ground.
The Department of Health said it had taken steps to protect whistleblowers.
A spokeswoman said: "This is the first government to set out proper legal protection for whistle blowers in the NHS.
"We expect a climate of openness and dialogue in the NHS and a culture and environment that encourages staff to feel able to raise concerns about healthcare matters sensibly and responsibly without fear of victimisation."