During a parliamentary debate on ending child imprisonment, justice minister Edward Argar admitted that the youth secure estate "requires real reform", but said that the system needs to retain custody as an option.
Argar said that depriving a child of their liberty was required "as a last resort", but added that there would be an emphasis on education at future secure schools for young offenders - the first being Medway.
Ex social worker and former shadow children's minister Emma Lewell-Buck gave an impassioned introduction to Tuesday's debate, claiming that prison is no place for children and suggesting that secure schools would be rebranded secure training centres.
The Labour backbencher highlighted a number of harrowing incidents involving the mistreatment of child prisoners, which have led in some cases to significant harm, and added: "I respectfully say to the minister that secure schools are not the answer.
"After all, 20 years ago that was what secure training centres were supposed to be but, as today's debate shows, they have evolved into something far uglier than their remit of excellence in care and education.
"Furthermore, having Medway as the experimental site for this new model is not only grossly misguided, but smacks of a lack of understanding of how culture, custom and practice infect an institution and never leave.
"Rebranding while the centre is still classed as requiring improvement for child safety will not lead to the improvements for which the minister hopes."
The MP for South Shields added: "I urge the minister to take serious action: abolish child prisons before more harm is done.
"It is not only his professional duty but his moral duty to do so."
Argar dismissed the claims, telling Lewell-Buck: "I respectfully disagree."
He added: "There will always be a need for a degree of security and a form of custodial setting.
"Alongside improving the existing estate, we are changing the fundamental approach.
"I believe that secure schools are the right way to proceed to ensure we move away from the concept of a prison with education to that of a school - an educational setting - with a degree of security. I believe that that strikes the right balance."
Lewell-Buck also asked about the phasing out of young offenders' institutions and STCs, promised by the government in 2016, but Argar ruled out providing a timeline before progress is made with Medway plans.
Responding to Agar's comments, Carolyne Willow, director of children's rights charity Article 39, said that the failure to give a timeline for closures suggested that the welfare and safety of affected children were "not registering as serious government priorities".
Willow added: "Two and a half years after accepting Charlie Taylor's recommendation that they be phased out, we need ministers to clearly set out their timetable for closing child prisons and building up the best of our secure children's homes."
Ross Little, chair of the National Association for Youth Justice, said: "Whilst encouraged by the evident cross-party support for Mrs Lewell-Buck's motion, we were disappointed and frustrated at the defensive stance adopted by the new Minister who appeared to be completely in denial about the depth of the ongoing crisis in our child prisons.
"The dangerous complacency of his statement (no doubt drafted by the same officials who have presided-over that crisis) shows exactly why many are now calling for the MoJ to be stripped of its responsibilities for all matters involving children."