Lack of maternity services putting patients at risk.

Maternity units are being forced to shut more often as the NHS comes under increasing pressure, the Royal College of Midwives (RCM) warns.

A midwives shortage is having a major impact and mistakes "will almost certainly be made", with patients put at risk, the union says.

A poll of 83 heads of midwifery at NHS trusts found a rise in the number of units that had closed their doors to mothers in need.A total of 42 per cent of units closed in the last year because they could not cope, up on 33 per cent the year before.

Units closed their doors on 6.6 separate occasions on average in 2014 and 4.8 separate occasions in 2015. One unit closed 23 times in 2015.

More than 90 per cent of the senior midwives said their unit was dealing with more complex cases than the previous year, while 30 per cent said they did not have enough midwives.

One in 10 (11 per cent) had to reduce services in the last year, including offering fewer parent classes as well as less support for bereaved parents and help with breastfeeding.

The RCM warns that services such as home births and postnatal care are also suffering as community staff have to cover gaps in hospitals. Midwives also have to leave postnatal wards - where aftercare to spot serious infections and breastfeeding support are offered - to help in labour and delivery suites.

Three-quarters of senior midwives said they had to redeploy staff to cover essential services.Many said they were unable to do their job to a standard they were happy with, while one in five had reduced staff training owing to other demands.

RCM chief executive Cathy Warwick, said: ""When services are operating at or beyond their capacity, safety is compromised and mistakes can, and almost certainly will, be made, through no fault of the dedicated staff delivering the service. This is simply not acceptable."

A Department of Health spokeswoman said: "We've invested in 1,900 more midwives and 3,600 more health visitors since 2010 and NHS England has commissioned a major independent review of maternity services for women and babies across the country."