The Southern Health and Social Services Trust had refused to force-feed the young woman - who was attempting to starve herself to death - saying she had the right to refuse nutrition.

However, in a test case for Northern Ireland, a High Court judge has ruled in her mother's favour and ordered medical staff to feed her immediately.

The 21-year-old, who cannot be named for legal reasons, has a long history of self-harm, suicide attempts and psychiatric admissions.

Described by medical staff as having a "severe emotionally unstable or borderline personality disorder", she was recently admitted to the psychiatric unit of Craigavon Area Hospital on a voluntary basis.

After threatening suicide and attempting to leave the hospital, she was detained under mental health legislation and transferred to St Luke's Hospital in Armagh where she began refusing food.

The court heard that her refusal to eat became her main focus and "the form of her ultimate self-harm".

Her mother begged the hospital to force-feed her.

But the Southern Health and Social Services Trust said that an adult " with capacity" has the right to refuse medical treatment.

They said that the provision of nourishment may amount to treatment, which means that the patient has the right to refuse it and the trust cannot intervene.

However, on day 26 of the hunger strike, Judge Mr Justice Weatherup said that the consequences of the girl's self harm are inevitably going to lead to deterioration of her physical condition as well as her mental condition.

He said that it would be incongruent if the girl could be detained in hospital without her consent for a mental disorder that involved self harming and that once detained she could continue self harming by going on hunger strike, but could not be treated without her consent.

Mr Justice Weatherup concluded that he was satisfied that in the present case it is lawful for the medical authorities to provide treatment for the woman by way of nourishment, without the patient's consent.

He said: "It is proposed to make a declaration that under Article 69 of the mental health (NI) Order 1986 it is lawful, without the consent of the patient, to provide treatment to the patient, in the form of nutrition, for the mental disorder from which she is suffering, when given by or under the direction of the responsible medical officer, as the nutrition will alleviate the symptoms and consequences of and prevent the deterioration of her mental disorder."

The woman, whose weight had plummeted to just six stone during her hunger strike, is currently recovering in St Luke's Hospital where her condition is improving.