Hospital units which care for Britain's sickest babies are facing cuts in nursing staff which are putting lives at risk, a survey has found.

A third of neonatal units in England are making nursing posts redundant, freezing vacancies or downgrading positions according to the survey by the charity Bliss.

The Royal College of Nursing described the situation as "desperate" adding that it was "deeply shocking" that posts should be cut when extra nurses were needed.

Last year, Bliss found neonatal units were more than 1,000 nurses short of the minimum staffing level set by the Department of Health. But, instead of increasing recruitment, the charity has found that a further 140 posts have been cut as the NHS seeks £20bn-worth of savings within existing budgets over the next four years.

"This comes after promises from the Government that nursing jobs would not be lost and that frontline services would not be affected in the drive to create efficiency savings," it says.

Neonatal units provide hi-tech care to the smallest babies, some born extremely premature, and need high levels of expert staff to carry out their responsibilities.

Yet one in 10 of the units said their training and education budgets had been cut and that they were unable to release nurses for training due to lack of staff. One in five units said they expected to make further staff cuts over the coming year. Andy Cole, the chief executive of Bliss, said: "The lives of England's sickest babies are [being put] at risk by needless cuts to the neonatal nursing workforce. The Government's assurances that frontline services would not be affected by changes in the NHS is not true for these most vulnerable patients. The Government and NHS must take responsibility now and ensure our tiniest and sickest babies receive the highest standard of care at this critical time in their lives."

The Bliss findings came from Freedom of Information requests sent to all neonatal units in England.

Janet Davies, director of nursing and service delivery at the Royal College of Nursing, said: "This report reflects the desperate state of affairs within neonatal units across the country. It is deeply shocking that, at a time when extra nurses are needed to meet even the most basic standards of neonatal care, some Trusts are making reckless cuts to posts, which will undoubtedly have an impact on the care of premature and sick babies. Sadly, this is a reflection on what is happening throughout the NHS, where we know that 40,000 posts are earmarked to be lost."

"It is critical that hospitals have the right numbers of specialist nurses who can provide one-to-one care to premature babies and support for families at an extremely stressful time in their lives. Equally, a properly funded strategy is now urgently needed to recruit and retain more of these specialist nurses."

Research by experts at the University of Oxford found that an increase in the level of specialist nurses in a neonatal unit is linked with a 48 per cent decline in the death rate among the babies.

Maintaining the correct level of staff on a neonatal unit allows nurses time to spend with parents explaining medical procedures and equipment and helping them care for their baby, which is key to a good outcome, Bliss said.

Anne Milton, the Public Health minister, said: "We want to make sure that sick and premature babies get consistently high-quality neonatal care. NHS hospitals in England must ensure that they have the right number of qualified staff to provide this.

"Our modernisation plans will cut the costs of administration by one-third over this Parliament, and every penny will be reinvested into frontline services."

Case study 'it was relentless'

Kieron Gray was born in Newham General Hospital in London in November last year at 24 weeks' gestation, weighing just 740 grams – less than a bag of sugar.

He was rushed to the Royal London hospital's neonatal unit, where he spent the first seven weeks of his life, while his lungs and other vital organs developed.

Vicky, his mother, said: "The staff were brilliant and so helpful. But you could see the pressure and stress they were under.

"Because Kieron's lungs were so bad, he was on a ventilator being given oxygen, and every time his oxygen level dropped a nurse had to adjust it. The nurses were constantly at the incubators, 24 hours a day, and they worked long shifts. It was relentless."

After seven weeks, Kieron was strong enough to be transferred back to Newham Hospital.

"The nurses there were wonderful too, but there were staff shortages," said Vicky. "There was one nurse to each room of four or five incubators, but often they had to look after two rooms because staff were absent. You could see they were under pressure. All the nurses agreed they needed more staff at the unit."