The birth of a baby is supposed to be a moment of joy. But for some medical staff it is the moment when they are most likely to be abused.

A survey of hospital staff has found that midwives experience more harassment, including verbal and physical assaults, than any other professional group, including doctors, nurses and health care assistants.

Tensions in the labour room are familiar to midwives, but the discovery that they suffer greater abuse in their working lives than other medical staff surprised experts. The harassment described included racial and sexual abuse as well as violence.

Dilys Robinson of the Institute of Employment Studies, which carried out the survey for NHS trusts in London, said: "People in labour can be in quite a state, and their friends and relatives can be in quite a state, too. Midwifery is a high-stress occupation, with patients and relatives panicking about emergency situations and things going on that they are not happy with."

The survey, to be published at the end of this month, monitors staff attitudes across a range of areas, including management, training and "sense of well-being".

Between 2000 and 2002 the institute collected 97,000 questionnaires from 99 London NHS trusts.

The results show that 38 per cent of midwives said they had experienced "some form of harassment or violence, including verbal, racial, sexual and physical abuse", compared with 36 per cent of hospital nurses, and 33 per cent of healthcare assistants. Doctors, administrative staff and other groups came lower down the abuse league.

Melanie Every of the Royal College of Midwives said: "We know that people get very tense during labour and women can be exceedingly abusive at times.

"Most midwives would accept that is part of the process. If the women remember they have been abusive - and many won't - they are usually very apologetic afterwards."

She added: "People in hospital are there because they are ill. Even when things are difficult they tend to be quite grateful. Pregnant women are not ill and their expectations tend to be higher."

Partners could become abusive if they were worried about their wife or girlfriend being in pain and felt not enough was being done to help them, the survey found. In London the problem was exacerbated by staff shortages which meant that midwives could be looking after three women at once.

"London is where the staff shortages are most acute, so this finding is not altogether surprising," Ms Every said.

Sheila Kitzinger, a childbirth expert and author, said: "We know that birth is a very intimate experience and a major life transition. People are more vulnerable to feeling they have been treated in an off-hand way, or processed on a factory belt, than if they had broken a leg. It seems to me the high level of harassment is quite logical."

Ms Kitzinger, who runs the Birth Crisis Network for women who have suffered traumatic births, said that the most common complaint from women was that they had been treated as "objects on a table" and like "oven-trussed turkeys."

Studies in Sheffield have shown the biggest cause of midwives leaving the profession is lack of satisfaction linked to a lack of interaction with the women giving birth.