The problem is particularly acute because of pressures on the NHS and because bullying may lead to staff quitting the profession. Staffing shortages have been blamed for the recent winter crisis in the health service.

Researchers from the Centre for Research in Health Behaviour at the University of Kent at Canterbury studied 1,100 staff at a community health trust in the south-east.

They asked staff about 20 different types of bullying behaviour, ranging from peristent attempts to belittle staff, unjustified criticism and putting people under pressure to produce work.

The biggest problems were 'shifting goalposts' and withholding information.

The staff most likely to report bullying were unqualified care staff and residential care workers, followed by nurses. Almost half of care workers said they had been intimidated, mostly by their managers.

"It is not surprising that more people lower down the ranks are bullied," said Lyn Quine, who led the research which is published in the British Medical Journal.

Lack of participation

Other research has shown high levels of bullying. A recent Royal College of Nursing report said one in three nurses had been intimidated.

The new research shows slightly higher levels.

Ms Quine said: "We know from some research that some work places and some factors influence bullying, for example, not being able to participate in the decision-making process or role ambiguity."

She added that the NHS had particular problems because it had been the subject of big upheavals in recent years and it was under great budget pressures.

She called on NHS managers to set up anti-bullying procedures and monitor carefully how frequently cases were reported.

Staff had to be assured their complaints would be investigated in confidence, she said. Managers also needed to be given support.

Disappointing

Health workers' union Unison said it was disappointed the research showed few improvements had been made since it did a similar study in 1997.

"Employers have to acknowledge the extent of the problem, set up procedures for dealing with it and train staff about it," said a spokeswoman.

"Employers have a duty to protect their staff. When these issues are left untackled they often fester and you end up with a very stressed workforce who have very low morale and do not do their jobs as well as they could."