Pregnant women could be turned away from closed maternity units unless action is taken to recruit more staff, the Royal College of Midwives (RCM) has warned.

The college said rising birth rates and an ageing workforce were leaving hospitals struggling to cope and many maternity units had too few staff.

A report by the RCM said an extra 5,000 midwives were needed in England to plug the gap.

It warned of 'massive' staff shortages as the rising numbers of midwives failed to keep pace with more complex births and a baby boom.

The number of births in the east of England increased by 21pc between 2001 and 2010 while the number of midwives increased by 18pc. The recommended ratio of midwives to births each year is one to 28, but all three Norfolk maternity units had not hit the targets, according to the latest figures released to the EDP by the hospitals.

At the Norfolk and Norwich University Hospital there were 5,093 births last year – a ratio of one midwife to 31 births.

The James Paget University Hospital, in Gorleston, and the Queen Elizabeth Hospital, in King's Lynn, were both one to 30. However, the West Suffolk Hospital was on target with a ratio of one to 27.

RCM manager for the eastern region, Pat Gould, said: 'There is concern about the quality of care that women will receive. We know in some units they have to close to admissions.'

She said when stretched maternity units closed, pregnant women were forced to travel miles to a different hospital at the last minute.

Prime minister David Cameron promised before the last general election that the Tories would increase the number of midwives by 3,000.

Belinda Phipps, chief executive of National Childbirth Trust (NCT), said: 'NCT supports the RCM's call for more midwives overall and, in particular, its analysis showing that expanded home birth and midwife-led unit services would take the pressure off over-stretched hospital staff and reduce the level of interventions for healthy women.'

A spokesman for the QEH in King's Lynn said: 'We have increased our numbers of midwives substantially in the past year. We have taken-on every recently-qualified midwife that has wanted to work here and we have recruited experienced midwives from across the south-east of England, the Midlands and from Ireland.

'We now have 103 midwives in post compared to 90 this time last year. When our latest recruits join us in January we will be fractionally below our target ration of 1:30 – one midwife for every 30 mothers in our area.'