By Matthew Chapman
BBC Five Live Report
A charity has called for independent advocates to be appointed in hospitals to act in premature babies' interests.
More premature babies now survive
Scope, which represents people with cerebral palsy, fears some babies are being denied life-saving treatment.
It says doctors and parents may be using statistics on the chances of extremely premature babies developing a disability to withdraw care from them.
Doctors said Scope's proposals would be unworkable because of the speed with which decisions often had to be made.
Recent research suggested babies born extremely prematurely have an almost 50% chance of developing a moderate to severe disability.
The charity's comments come as the respected Nuffield Council on Bioethics carries out a public consultation on the way extremely premature babies, born at less than 28 weeks gestation, should be treated in the NHS.
Among the questions the consultation is asking is whether the economics of treating and then bringing up a disabled child should be a factor in decisions made by doctors and parents about whether to continue treating very sick babies.
Babies turned away
Doctors say, in some cases, they are having to turn away from busy neo-natal intensive care units babies who have a good chance of survival because incubators are being used by extremely premature babies who have significantly lower life chances.
A recent survey by the premature baby charity Bliss found 70% of neo-natal units have had to shut their doors to new admissions at some point in the last six months.
The charity called for the appointment of 2,700 extra nurses.
Richard Parnell, head of research and public policy at Scope, said: "I think Scope's major concern about this debate is who actually acts in the interests of the child."
Parents of extremely premature babies and doctors will often hold conferences before the birth or within hours of birth to decide whether to continue with intensive care.
Mr Parnell said that wrongly saw disability as a "risk" and so looked at how wanted the child was before making a decision.
"I have spoken to paediatricians who take into account the circumstances of the family, if the family has more than one child, if the birth is unplanned then that would influence them one way, and if the birth was planned and very much wanted that would influence them another way.
"That raises huge concerns in my mind about who is acting in that child's interests."
Survival rate growing
Only about a quarter of babies born at less than 25 weeks live, although that is four times as many as compared with 20 years ago.
Medical advances mean that some are even surviving when born at 21 or 22 weeks.
Until recently, no-one really knew what their long term prospects were.
The Epicure study has been following the lives of 300 extremely premature babies over six years and has found that just under half have developed a moderate or severe disability including cerebral palsy and autism.
Doctors have said Scope's suggestion would be unworkable as sometimes decisions have to be made within minutes.
"Sometimes it's a very fast moving situation and you really can't wait around," said Professor Andrew Whitelaw, head of neonatology at the University of Bristol.
"In any case I would say the doctor is always advocating what is best in the interests of the child so there is no need for another person to be involved."
One mother described to BBC Radio Five how her son born at 24 weeks gestation was given life-saving steroids.
Now, five years later, he has developed severe autism, which has had an enormous impact on the family.
When asked whether she thought the right decision had been made to give life-saving treatment to her son, she answered, "I don't know. I love my son to bits, but it has been a very long, very hard, very tough five years.
"There have been times when I wonder whether we did him any favours and there are times where I dread to think what the future holds for him."
She said more investment needed to be made into supporting parents coping with bringing up disabled children.
Matthew Chapman's report, Too Young to Live, can be heard on Five Live on Sunday 31 July at 1100 BST and 1900BST and after that at the Five Live Report website.