According to a new report by the Prisons and Probation inspectorates, facilities are failing to prepare children to live safely when they're released.
Most young offenders have no training, education or employment arranged and mental health support is often "lacking".
It has also claimed that in many cases suitable housing is not in place.
Caring for Ex-Offenders is initiative by London church Holy Trinity Brompton that helps former inmates reintegrate into society.
Speaking to Premier, Caring for executive director, Paul Cowley said prisons are already taking positive steps to provide better support, but funding needs to increase.
He said: "They have hired over 4,000 new prison officers, but that will take a while to get into the system, more education. And basically, it sounds like the same old thing is needed - more money for our prison system."
Cowley thinks the UK prison system needs to be re-considered: "We have to rethink how we run prisons, when we look around the world at the way prisons are run, especially the Scandinavian countries, how they treat people in prison, it's very different to the way we treat them. Ours is a little bit archaic still."
There are also concerns that a lack of adequate support will contribute to re-offending rates.
According to statistics for April 2016 to March 2017, some 70 per cent of children re-offended after release when serving a sentence of under a year.
More than half re-offended on release after serving a longer period behind bars.
Paul Cowley said: "The report highlights some areas that are being addressed by the prison, trying new sports initiatives and so on, but it's down to the outside agencies as well. Personally, I think that they're not always as connected as they could be."
"There's lots of things that need to be looked at. But Christians can get themselves inside the prisons, go and visit, they can help or get involved in mentoring programmes, they could help on an Alpha team. Just give it a go.
"And of course, when these young kids get released, they can encourage them to be part of a community where the Christian church is a family."
"Christians in the prison system are doing fantastic things, but we could do more, and especially outside when these people are released."
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