Inadequate staffing levels are driving midwives to leave the NHS, with some looking after as many as 15 mothers and babies at a time, a report has found.

The study of more than 2,700 midwives uncovered fears about making mistakes because they were working 12-hour shifts with no break.

Midwives reported not being listened to when they told managers they feared for the safety of mothers and babies, while others experienced bullying from senior staff.

The respondents to the poll, for the Royal College of Midwives, were made up as follows: 31% were midwives who have left the profession in the past two years and 69% were intending to leave in the next two years.

The top reasons for leaving were not being happy with staffing levels at work (52%), not being satisfied with the quality of care they were able to give (48%) and being unhappy with the workload (39%).

A third (35%) were unhappy with the level of support from their managers while 32% were unhappy with working conditions.

Of those who intended to leave the profession, 62% were unhappy with staffing levels, 52% were not satisfied with the quality of care they were able to give, 46% were unhappy with the workload, 37% were unhappy with conditions and 30% did not agree with the model of care they had to work in.

When asked if they might return to midwifery, only 18% said they would consider doing so.

When asked to expand on their experiences, one midwife who left more than 18 months ago said she was stressed “trying to provide good as well as safe midwifery care despite ridiculously low staffing levels and having to complete endless paperwork just to prove I was there”.

Others reported feeling depressed and under-valued, while one who intended to leave midwifery in the next 12 to 18 months said: “I am tired and worn out and am concerned that if this continues that I might make a tragic mistake.”

A midwife who left after 40 years said the “stress of under-staffing and the ever-increasing workload” had left her burnt out.

One who left the profession in the past six months said: “I was often working 12.5 hours with no breaks. My unit was struggling with employing enough midwives – we had a shortage of 30 full-time midwives in the unit. I was not able to deliver the care I wanted as decisions were often made about women’s birth without her full involvement.

“It was not safe to look after 15 mums and babies on a postnatal ward by one midwife. We were not listened to when we raised issues over staffing and safety.”

Others described in detail “dangerous and unsafe” working conditions.

One who left more than six months ago said: “I felt scared with the care I was able to deliver. I was left in a dangerous position on many occasions due to a lack of staff and a lack of support from managers when escalating concerns.”

Another said: “Maternity is the most litigious area in healthcare, yet we cannot actually practice safely and in a way that makes us proud, due to chronic staff shortages and cost-cutting.”

Some midwives with young children said their applications to work flexibly or part-time were denied, forcing them to leave. Others described bullying bosses and said they were working in a “culture of fear”.

One said: “Changes are put in place after serious incidents – ie more staff in those specific areas – but as soon as the workload reaches capacity these staff are moved to cover other areas once again leaving you in a vulnerable position.”

Another said: “I have seen midwifery colleagues destroyed by management if something goes wrong and yet they had worked 12-hour shifts without breaks and no one will accept that the system has caused the failure.”

Cathy Warwick, chief executive of the RCM, said the findings were “saddening, dispiriting and worrying”. She added: “Maternity services are performing as well as they are on the backs of the selfless dedication of midwives and other maternity staff, and their capacity to go that extra mile for mothers and babies, day after day. However, this shows that many cannot fight that battle any longer.

“Enormous demands are being made on midwives and the services they work for, yet investment in these services from the government remains inadequate to provide the quality of care that women deserve.”

The RCM has repeatedly called for more midwives, saying there is a shortage of 3,500 across the NHS.

Conservative MP Dr Dan Poulter, who was the maternity services minister in the coalition until May 2015, said that the risks involved in delivering babies could be prompting some midwives to leave.

“Delivering babies is a very rewarding job, but also a very risky one, so it is unsurprising that chronic understaffing in some already overstretched maternity units is resulting in midwives feeling unable to deliver safe care to the women they are caring for. It is perhaps unsurprising that this has resulted in a demoralised maternity workforce,” he said.

Jonathan Ashworth MP, Labour’s shadow health secretary, said: “This is yet more evidence of the staffing crises in the NHS affecting staff morale and patient care. Midwives want to do the best for their patients but as this survey shows, pressure on services and staff shortages mean too many are unhappy with the quality of care they are able to give. The government needs to do something to relieve this crisis and ensure that no exodus occurs that will make the current situation even worse.”