LONDON - The safety of premature babies could be at risk because of staff shortages and lack of cots in specialist units, a report by an independent watchdog said on Wednesday.

The National Audit Office (NAO) found that, on average, the country's 180 neonatal units had to turn away new admissions once a week because of the problems, and said death rates varied widely depending on where the babies were born.

"It is shocking to hear that the safety of ill and defenceless babies is being compromised by a significant shortage of nursing staff," said Edward Leigh, chairman of parliament's Public Accounts Committee, to which the NAO reports.

"And even more worryingly, babies are unable to receive the right levels of intensive care because of a lack of cots or overcrowding."

Every year about 10 percent, or 60,000 newborn babies require specialist treatment and the number is increasing, the NAO said, because of factors such as a rise in older mothers, obesity and the use of assisted conception.

The Department of Health reorganised neonatal services in 2003 to increase the number of cots and reduce long distance transfer of mothers and their seriously ill babies.

However, the NAO report said while services were improving there were still problems, mainly a lack of cots available for the level of care required, and a shortage of qualified neonatal nurses.

The watchdog said each unit had nearly three neonatal nurse vacancies, and that the vast majority of intensive care units, which require a ratio of one nurse for one baby, failed to meet the necessary standard.

Nearly a third of units had to care for a baby that should have been transferred for more specialist care but could not be because no cot was available. Three units were operating above 100 percent occupancy rate.

"High occupancy rates could have consequences for patient safety, for example due to increased risk of infection or inadequate levels of care," the report said.

Transport still remained a problem, with only half of neonatal networks providing specialist services between units 24 hours a day, seven days a week.

The NAO also noted a wide variation in mortality rates, with 1.8 deaths per 1,000 live births in Surrey and Sussex, but 4.8 in the southwest Midlands.

Dr Sheila Shribman, the government's Clinical Director for Maternity Services, said neonatal networks were "working hard" to recruit and retain staff, and free up specialist nurses for cot-side care.

Campaign group Bliss said the government should act urgently on the report.

"The report confirms that babies are not receiving the same level of care as children or adults -- a situation that BLISS has been campaigning to change for over three years," the charity said in a statement.