Minister for Children and Youth Affairs Frances Fitzgerald has said there has been an increase in demand for places for juvenile offenders in recent years.

The minister said the Government is "working actively" to open a new eight-bed unit in Oberstown, Co Dublin to meet the current demand.

Speaking on RTÉ's News at One, the minister said that in 2011 there had been just 11 detention places available in St Patrick's Institution.

Since its closure last year, the minister said the number of places available increased to an average of 21 in Oberstown last year and this week there are 36 spaces available.

The minister was responding to criticism by Judge Ann Ryan that the Government is not providing enough detention places for juvenile offenders.

Ms Fitzgerald said that the availability of places is flexible.

She said that had the child, whose case was being dealt with by Judge Ryan, appeared in court today, there would have been a space available.

At the Children's Court, Judge Ryan told officials from the Department of Children and the Irish Youth Justice Service that it was not good enough that the Government was having audits, meetings and reviews about the matter.

The judge had asked to see Minister Fitzgerald, but instead two officials from her department and the Youth Justice Service went to court to explain the lack of detention places.

They said that an existing eight-bed unit was closed because of staffing difficulties and that a new detention facility on adjacent land would be ready by the middle of next year.

But Judge Ryan said those explanations were not good enough.

"Get those eight beds open now please," she said.

Later, the young boy who was the subject of the judge's comments was arrested and brought before the Children's Court on foot of a bench warrant.

A bed became available in Oberstown Boys School and he was remanded in detention to next Thursday.

Judge warns children could be released to commit crimes

On at least 18 separate occasions in the last three weeks, the court has been unable to detain children charged with or convicted of serious offences because of the lack of detention spaces.

Nine children, some of whom repeatedly breached their bail conditions and one who has been warned by gardaí that his life is in danger, could not be remanded in custody.

Judge Ryan said that putting a child in detention was the last resort and a decision not taken lightly.

Children's courts all over the country are faced with the situation where they are letting a child who was in detention go free where they could commit some awful crime, she said.

Minister Fitzgerald last year ordered that children under 16 should no longer be sent to St Patrick's Institution, but work on a proposed new detention facility at Oberstown has not yet begun.

The Department of Children and Youth Affairs has said the money for Oberstown has been secured and the building project will begin in July.

Two units will be available by the middle of 2014.