Britain is falling short of obligations set out under international law for dealing with migrant children who arrive in the country without parents or relatives, a group of parliamentarians has warned.
Immigration concerns are too often given priority over the protection of unaccompanied migrant children, including abuse victims and those who have fled conflict zones, the Joint Committee on Human Rights found.
The Committee said the UK is as a result failing to meet the terms of the UN Convention on the Rights of the Child, a treaty bound by international law.
It also calls on the Government not to return any children to Afghanistan or Iraq while conflict and humanitarian concerns persist.
In 2012, around 1,200 such children sought asylum in the UK, and around 2,150 unaccompanied migrant children were being cared for by local authorities.
Committee chairman Dr Hywel Francis MP said: "Unaccompanied migrant children in the asylum and immigration processes are some of the most vulnerable young people in the United Kingdom.
"They have often fled conflict situations abroad or have been victims of abuse and exploitation, including those who arrive as victims of trafficking.
"It is crucial that they are supported effectively. We do not find it satisfactory that immigration concerns are too often given priority when dealing with such children, in doing so the UK is falling short of the obligations it owes to such children under the UN Convention on the Rights of the Child."
Children who had often faced traumatic journeys faced intensive interviews on arrival for which there were too rarely interpreting facilities available, the Committee said.
There was also evidence of children being placed in inappropriate accommodation without suitably trained staff, which was a point of particular anxiety where children were victims of trafficking.
The Committee, which is made up of MPs and peers, said a lack of support was "starkly" demonstrated by the "culture of disbelief" about the age of unaccompanied asylum-seeking children.
It found that the age of unaccompanied migrant children is too often disputed, putting their welfare and best interests at risk.
The group has called for a change in emphasis to put the best interests of unaccompanied migrant children at the heart of the complex and stressful asylum and immigration processes affecting them.
The Committee's report also said decisions on children's futures are too often delayed until they approach adulthood, leaving children uncertain about what their futures will hold.
And the Committee also wants the Government to set up pilot programmes in England and Wales to appoint guardians for unaccompanied migrant children to fight for their best interests and offer them support.
Kamena Dorling, manager of the Migrant Children's Project at Coram Children's Legal Centre and co-chair of the Refugee Children's Consortium, said: "Unaccompanied refugee and migrant children have often been through experiences unimaginable to most of us.
"They are alone in the UK with no one to care for them. The Committee's report is a timely reminder that the UK is still failing to meet its legal obligations to these children.
"Too often their rights are not realised in practice and they are denied the support and protection they so desperately need.
"It is long overdue that children's best interests are truly put at the heart of all decisions made about them, whatever their status. It is vital that central and local government take real and prompt action to implement the many practical and systemic changes needed, as recommended in this important report, so that we do not continue to fail these children."
A Home Office spokeswoman said: "The UK takes its international responsibilities to children seriously and their welfare is at the heart of every decision made.
"Unaccompanied asylum-seeking children are always given individual support and reassurance from those in social services and immigration.
"Age assessments are vital in ensuring that children and adults are treated appropriately as unfortunately adults claim to be children in order to access this specialist support.
"Rightly, local authorities are responsible for making this decision - as they need to make sure that adults are not placed in accommodation with vulnerable children."