Syrian refugee children who use services on both sides of the Irish border could fall victim to a no-deal Brexit, a charity has warned.
Youngsters from outside the European Union (EU) or UK and suffering from severe trauma, abuse or substance abuse are cared for at residential homes on an all-Ireland basis to produce economies of scale.
They would not be covered by freedom of movement provisions which pre-date the EU and will ensure free passage of most people between Northern Ireland and the Republic after March's divorce.
A charity consultant, who asked to remain anonymous, said: "We are used to being stoical about Brexit."
He added: "We are concerned about what the future is for cross-border movement for those kinds of service users."
He said a number of charities worked with people from Syria, migrants from eastern Europe and families from the Middle East or Africa.
Some have mental health issues, have abused substances or suffered other forms of trauma.
The consultant added: "Charities work on an all-island basis, you send service users across the border to facilities.
"If those service users are not EU nationals or UK nationals, when the border comes, does that mean we cannot take someone who lives in the south into the north?"
He added: "These are children in crisis and adverse circumstances.
"Over the last decade the charity has developed an all-island approach, economies of scale in the supply of residential facilities."
The first Syrian refugees participating in the UK's Syrian Vulnerable Persons Relocation Scheme arrived in Belfast in December 2015. Hundreds have entered since then.
The charity consultant addressed a meeting on Brexit at the offices of the Northern Ireland Council for Voluntary Action (NICVA) in Belfast.
NICVA's head of policy and public affairs Geoff Nuttall said: "What happens to services that straddle the border in a no-deal scenario?
"One of the case studies from Women's Aid (which helps victims of domestic abuse) was talking about, at the sharp end, women seeking help who may be in households that they literally have to leave and go to the nearest support, that support could be over the border, the nearest one."
He also raised the prospect of ambulances stopping at the border and patients being picked up at the other side.
"There are lots of issues around the supply of drugs, licensed drugs, lots of health concerns generally.
"Environment is the other area that is so bound up with European policy frameworks and enforcement that replacing that is such a major issue, everything from illegal waste to pollution, to how we manage every aspect of the environment is all up in the air."
Mr Nuttall said the overall impact of a no-deal Brexit on the economy, cross-border trade and public finances was worrying.
"There are going to be potentially direct effects on people in our sector who are providing services for the most vulnerable who are already under enormous budgetary pressures.
"It is the destabilising effect on the economy and on the rights and protections that organisations are highly concerned about."
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