The Government is planning to use the new Thornton Hall prison to accommodate young offenders who are still legally children, in breach of an international treaty which prohibits the jailing of juveniles in adult places of detention.
The new prison will include spaces for teenage offenders aged between 16 and 17 years of age, most of whom are accommodated in St Patrick's Institution for young offenders.
However, St Patrick's - part of the Mountjoy Prison complex - is due to be demolished once Thornton Hall is completed and no child detention facility will be available to take these young offenders.
A spokesman for Minister for Justice Brian Lenihan confirmed that the new prison will admit young offenders. However, he insisted this would be done as an interim measure.
A major new child detention facility is being planned which will ultimately accommodate almost all of the State's young offenders and remove children from the prison system.
An expert group involving a range of Government officials is understood to have recommended a major new child detention school-complex be built in Lusk, Co Dublin, The Irish Times has learned.
The report was completed in recent weeks and the recommendations are expected to go before the Cabinet in the early part of this year.
The complex, which could cost in the region of €140 million, would accommodate more than 100 offenders aged between 12 and 18 who are accommodated in facilities such as St Patrick's Institution, Trinity House, Oberstown centre for boys and girls and the Finglas child and adolescent centre.
Meanwhile, the Government move to locate teenagers in Thornton Hall has attracted strong criticism from children's rights campaigners.
Fr Tony Riordan of the Jesuit Centre for Faith and Justice said there was no need for a facility for young people in Thornton Hall which would not be equipped to meet the need of young people.
Instead, he said the Government should enhance St Patrick's Institution and staff it with a properly-trained childcare team, when there are no longer adult prisoners in Mountjoy.
"The detention of young people who are still legally children in adult prisons has been one of the most shameful features of the Irish penal system," he said. "The Government has given repeated commitments to end the practice of detaining those under 18 alongside adults."
The Children's Rights Alliance and the Irish Penal Reform Trust have also expressed concern about the plans. They described the move as a retrograde step and expressed concerned that the plans may delay progress on the proposed new child detention school complex.
The expert group examined a range of options and locations for a new multimillion euro facility.
A spokesman for Minister for Children Brendan Smith refused to comment on the report's recommendations, except to say that the Minister received the report in recent weeks.
However, well-placed sources say the expert group settled on Lusk for a range of reasons, including the supply of State-owned land to develop the complex and the three child detention schools are already located in the area.
There is no estimated date for the construction of the campus. Consequently, it seems likely that the controversial practice of jailing teenagers in adult places of detention will continue for some time.
In 2006, a total of 165 young people under the age of 18 were imprisoned in adult jails.
This practice is in contravention of the UN Convention on the Rights of the Child.