Children's charity Barnardo's is facing criticism for agreeing to to run welfare services at the government's proposed removal centre for refused asylum seekers.
The UK Border Agency is converting a special needs school near Gatwick into a detention centre for families and children.
The Home Office's new system is aimed at putting further pressure on people seeking asylum.
Barnado's says it believes its presence will help hold the Home Office to a commitment to run a more humane removal system.
But campaigners for asylum seeker and refugee rights say that its involvement will amount to collusion in an unjust and inhumane system.
The Rev Vaughan Jones, who is a United Reformed Church minister, the CEO of multi-agency NGO Praxis, and an associate of the beliefs and values thinktank Ekklesia, expressed his dismay at the charity's move today.
"There will be considerable disappointment that Barnardo’s has lent its distinguished name and reputation to this highly unsatisfactory replacement to the appalling practice of detaining children," declared Jones.
He continued: "The move toward prison by another name has not been accepted as a proper solution by those who have the best interests of children at heart. Barnardo’s seem to have agreed to be part of the imprisonment itself and will inevitably be identified as part of the system rather than advocates for children in desperate circumstances.
"As things stand with displaced communities, the new arrangements lack credibility among refugee and migrant civil society and we can only hope that the pressure remains especially upon the Liberal Democrats. They gained respect for their enlightened view but have not delivered on this fundamental issue of the human rights of a child," he said.
"We are being let down by an organisation which can be justly proud of the work it has undertaken with asylum seeking children in the past," concluded Vaughan Jones - a former Barnado's employee himself.
Praxis (http://www.praxis.org.uk/) is a London-wide NGO committed to "being with displaced communities, listening and acting through our common humanity to create and nurture reconciliation, human rights and social justice."