A Dublin couple who lost their case for negligence against the National Maternity Hospital are now facing a legal bill of up to €500,000.

Linda and Anthony Duffy took the action after their now ten-year-old son contracted meningitis as a premature baby, leaving him with severe brain damage.

In court today, Mr Justice Sean Ryan told the couple he had no choice but to order them to pay half the hospital's costs.

The hospital had sought all its costs.

The court heard that the family home is the only asset of Mrs Duffy, a primary school teacher, and her husband Anthony, who works in property maintenance.

The Cabinteely couple has three children, the eldest of whom is Mark, who is profoundly disabled and requires 24-hour care after suffering severe brain injuries and loss of an eye after contracting meningitis after his premature birth.

While the normal rule requires costs to go to the winning side, the judge said he was reducing the costs order to 50%.

This arises from an "extremely rare and unusual development" where the NMH raised an issue during the case which delayed it for up to five months and was ultimately not pursued.

While he was not according any blame to the NMH for raising the issue, it had added to the stress and worry experienced by the parents as the case, which began in November 2011 with judgment last August, was delayed.

The judge stressed he was very sympathetic to the parents, very much admired them and their son, and was very troubled by all the matters raised on their behalf in opposing costs.

He said if there was any way he could legitimately avoid awarding costs against them, he would do so, but under the law felt he had no choice.

Earlier, seeking all the NMH costs, Patrick Hanratty SC said the normal costs rule should apply and the fact the NMH had to investigate an issue which delayed the case for a period should not affect that.

Resisting the costs application, Bruce Antoniotti SC for the parents asked the judge to make no order for costs, meaning each side pay their own.

This was not an unmeritorious case and his clients had relied on the views of world-renowned experts when deciding to bring it, he said.

He said the parents had an obligation to pursue any means of providing for their severely injured child's security into the future.

Mr Antoniotti also referred to another judge's decision in a commercial case where just some of the costs were awarded, but Mr Hanratty argued that provided no grounds for not adhering to the normal order that costs go to the winning side.

Outside court, Mrs Duffy said they were "devastated" at the costs ruling, which would add to the enormous pressure they were under in seeking to ensure their son received appropriate care.

She said the situation now is that he does not get consecutive care and has ended up in hospital due to breaks in care.

Mr Duffy said they woud consider appealing the judge's dismissal of their action, and the costs ruling.

They had no choice but to bring the case in order to see what went wrong resulting in their son's serious injuries, he added.

Last August, Mr Justice Ryan dismissed claims of negligence by the hospital in the treatment of Mark.

He rejected arguments by experts for the parents that the hospital should have suspected Mark had meningitis and should have carried out a lumbar puncture - the test to confirm or exclude meningitis.

In a lengthy judgment analysing the evidence for both sides, the judge ruled the evidence did not establish any failure of care or negligence by the hospital in its treatment of Mark.

Mark was born prematurely at the NMH on 18 July 2002 by caesarean section after 30 weeks gestation.

The judge said his premature birth and very low birth weight made him vulnerable to infection and, in his second week of life, he contracted meningitis which caused severe brain damage and left him with permanent physical and mental disabilities.

The action centred around Mark's treatment on 30-31 July 2002, which experts on his behalf claimed was sub-standard.

The judge concluded the evidence did not establish negligence or a failure of care because the doctors treating Mark at the NMH did not do a lumbar puncture.

He accepted evidence, when Mark was presented to the doctors, there was nothing to suggest a likelihood of meningitis and said it was reasonable for the NMH to wait and see how the situation developed.