The parents of critically ill baby Charlotte Wyatt today lost the latest round in their continuing battle to keep their daughter alive, following the ruling of a high court judge.

Judge Mr Justice Hedley rejected their appeal to overturn an earlier court order allowing doctors to let her die if she stops breathing.

But he said the order was not open-ended and remained subject to review.

He told the high court in London this morning: "I am quite clear that it would not be in Charlotte's best interests to die in the course of futile aggressive treatment."

He said that in the event of respiratory collapse, all treatment up to but not including intubation and ventilation would be in Charlotte's best interests, "but nothing further".

The ruling follows an earlier court case last October when doctors at St Mary's hospital in Portsmouth won the legal right not to resuscitate Charlotte - now 18 months old - after arguing that her brain and other organs were so seriously damaged that she had "no feeling other than continuing pain".

Her parents, Debbie and Darren Wyatt, went back to court last month to appeal against that decision arguing that since the autumn their daughter's condition had improved.

The family's case focused on evidence from six independent medical witnesses that their daughter was not in pain, is aware, alert, active and responsive.

Charlotte weighed 1lb and measured only five inches when she was born three months prematurely in October 2003. She has serious brain, lung and kidney damage.

Today Charlotte spends most of her time in an oxygen box, but is taken out to be cuddled by her parents when they visit

Doctors still insist that resuscitating her if she stops breathing would be "pointless and possibly inhumane" because it would only prolong her suffering.

Explaining his decision, Mr Justice Hedley said he was delighted that Charlotte had survived the winter but told her parents she was still a "terminally ill child".

He told the court that she still required 50% oxygen and would not be able to return home unless that was reduced to 30% or lower.

Charlotte's ability to respond to loud noise and track the movement of a colourful toy was in contrast to her condition last October when she was almost wholly unresponsive and required almost constant sedation. Her life now could no longer be described as intolerable, he said.

But her chronic respiratory disease was still expected to be fatal and her neurological condition was as bad as it could be. Her head was still the size of a newborn baby and there had been no brain growth.

Fed continuously through a tube, she was seriously undernourished. She remained "a terminally ill child", the judge said.

The lawyers representing Charlotte's parents announced they plan to appeal against the high court decision and go the court of appeal.

They said that Debbie and Darren Wyatt were "very unhappy" with the judge's decision.

Earlier today Mr Justice Hedley said that he accepted that the next time Charlotte faced another medial crisis her case would have to return to court because her parents and doctors were unlikely to agree over her treatment.

He told the court that the hospital where Charlotte is being cared for did not have the necessary intensive care facilities and, if none were available at Southampton, a country-wide search would have to be conducted.

Charlotte, under sedation and being intubated and ventilated, would become "more an object to whom things are done than a child".

"No one would ever willingly put a child through that if no purpose was to be served and it is easy to see that it is inconsistent with a peaceful death," he said.

Ruling that he should make a decision now, the judge said it would be wholly contrary to the baby's best interests for a crisis - which was highly likely to be brought about by respiratory infection - to be "overshadowed by a major legal conflict".

He added that the decision, at the time of the crisis, on whether to rely on the court declaration allowing doctors to withhold ventilation must be taken by the hospital on the basis of Charlotte's best interests and in close consultation with the parents.

The judge said relations between the parents and the hospital were very fragile. When Mr Wyatt visited, he was accompanied at all times by a member of the security staff. This "does not betoken harmonious relationships".

Hospital staff were clearly very stressed by the enormity of Charlotte's plight and the volatility, as they saw it, of the parents.

Explaining how he reached his decision he said everyone agreed that every reasonable step short of major invasive treatment should be employed to sustain her life. Only one doctor felt that further steps should be taken.

The judge said he was convinced by the majority medical opinion. Charlotte was unlikely to survive a major crisis and, even if she did, her condition would deteriorate to a point where her life would be intolerable. She would probably not return to her present improved condition.

The judge said he would review the case again, probably in October.

Reading out a statement on behalf of the parents outside the court, their solicitor, Richard Stein, said: "Darren and Debbie are very disappointed that the judge has confirmed that as things stand, Charlotte will not be ventilated in the event she requires it.

"He did, however, recognise that her condition has changed significantly - in fact, it continues to improve.

"For example, only five weeks ago, there was evidence before the judge that she was badly malnourished and only today we heard from the trust that she had put on significant amounts of weight over the last four weeks.

"The judge is clearly concerned about the uncertainty of her future. He has ordered that the case be kept under review and allowed Darren and Debbie to appeal to the court of appeal, which is something they greatly welcome."

Asked if he was disappointed with today's outcome, Mr Wyatt said he had no comment.

Charlotte's grandmother said today she supported the doctor's decision that it was not in her granddaughter's interest to be resuscitated if she stopped breathing.

Julie Wyatt, from Tamworth, Staffordshire told BBC WM: "I don't think she would ever be able to walk or maybe even eat properly on her own even though she is being spoon-fed at the moment, just tiny bits.

"I don't think she would grow up to be a perfectly healthy child. I think she would be a lot of work for the parents.

"Myself, I'm trusting the hospital decision at the moment because I've seen the care they've given her and I know they love her, they've been with her 17 months of her life and I think they love her and they don't want nothing to happen to her.

"They are not withholding any treatment at all and I do believe that if they don't resuscitate her, it is for Charlotte's best interests, to be quite honest."