Special care baby units are further than ever from reaching recommended staffing ratios, a study has suggested.
Premature babies often need special care
Bliss, the premature baby charity, warned the service was acutely understaffed, and new funds were urgently needed.
It said units were sometimes forced to close, leaving babies to travel long distances for appropriate care.
The government said more neonatal intensive cots were now available, but admitted there were localised problems.
Every year more than 80,000 babies in the UK are admitted for care in specialist neonatal units.
The latest report shows that, on average, units were understaffed by over a third.
Over six months, neonatal units were shut to new admissions for an average of 24 days.
While demand exceeds capacity across all levels of care, the greatest pressure was on intensive care.
Two-thirds of units providing the full range of intensive care did not have enough staffed cots for the babies admitted, and one in ten units exceeded its capacity for intensive care for over seven weeks in a six-month period.
The study also found a quarter of twins or triplets were reported to be cared for in separate hospitals.
A recent study showed that if each baby in specialist intensive care received one to one treatment, infant deaths could be cut by 48%.
However, the Bliss study suggests only 3.8% of units currently achieve this recommended level.
Andy Cole, Bliss chief executive, called on ministers to make one-to-one nursing care mandatory for intensive care babies.
He said: "The first few days after birth are absolutely critical for babies born premature or sick, and the care they receive during this period shapes not only their chances of survival but also their future health.
"Bliss is concerned that the government gives less priority to intensive care for babies than for adults and children, and that it is only thanks to the goodwill and commitment of doctors and nurses that babies are being cared for in some cases."
Health minister Ivan Lewis said: "There is nothing more important than the care and support we offer to sick babies and their parents.
"That is why we created neo-natal networks in response to the frequent mismatch between the number of cots available and babies requiring care."
Mr Lewis said between 2003/04 and 2005/06 there was an increase of over 13% in the number of neonatal intensive cots available nationally.
However, he added: "We acknowledge that in some localities there are still concerns."
He said work would continue to examine the effectiveness of existing neonatal care networks, the availability of cots and related workforce issues.