Charity Mencap said today it was "appalled" by reports that an autistic woman is to be moved from Swansea to a specialist unit in Brighton.
Claire Dyer, 20, will have to move from the unit she has lived at since April 2012 after Abertawe Bro Morgannwg University Health Board's decision was upheld by a judge, according to the BBC.
Her family obtained an injunction blocking the move but it was overruled at a hearing today, the report said.
The court was told the board had proposed the transfer because staff cannot cope with Miss Dyer's "extremely challenging" behaviour and there was no suitable alternative in Wales, it added.
Catherine Dyer, of Gowerton, said she fully understands her daughter needs care, but believes Brighton is too far away and will make her daughter's behaviour worse.
She said: "We are heart-broken and devastated that my daughter is to be moved 230 miles away and this decision will just tear our family apart.
"We are totally against Claire being sent hundreds of miles away to Brighton, not just because of how far away it is from her family, but also because we do not believe that a medium secure hospital is suitable to meet her needs."
Mencap said it understood the case was at the High Court in London.
Wayne Crocker, director of Mencap Cymru, said in a statement: "Mencap is appalled by the decision today to allow Abertawe Bro Morgannwg Health Board to send Claire Dyer to an assessment and treatment unit many hundreds of miles away from the family that loves and supports her.
"We want to see an end to the unacceptable culture of long-term placements in inpatient units, often hundreds of miles away from their homes, where people are at significant risk of abuse and neglect. This can cause huge distress, and there is no doubt that this is the case for Claire and her family.
"Governments - whether in England, Wales, Scotland or Northern Ireland - must be committed to providing quality support and services for people like Claire in their local community."
The health board said in a statement: "W e make every effort to arrange temporary placements as close as possible to the patient's home so their family is near. Unfortunately this is not always possible because the specialist facilities needed are not available locally.
"Patients with very complex individual conditions may need a specialist assessment, which for safety reasons often needs to be carried out in a secure environment.
"When an assessment is needed we always begin by contacting the specialist services closest to the patient's home. Unfortunately, on some occasions we are unable to find a service in Wales able to provide the highly specialist assessment, care and security needed.
"Should this happen, we then approach specialist services in England. We are very much aware of the distance this can place between a patient and their family.
"However, the assessment is critical and the placement is seen as temporary. We then plan for the patient to return closer to home as soon as possible."