Prison bosses have revealed that the super jail in Peterhead is now running at almost full capacity.
Staff at HMP Grampian encountered problems after opening in 2014 due to a riot just days after prisoners were moved into the building.
Young offenders were moved down south and the Ellon youth wing closed.
An annual report published by the Scottish Prison Service (SPS) has now shown that there is an average daily prisoner population of 445 adult inmates, with only 29 spaces free.
More places would be made available at the £140million complex if the Ellon youth wing, which was closed following the disturbance four years ago, was reopened.
The prison could house more inmates if the whole of the building was in use.
Liam Kerr, Scottish Conservative justice spokesman, said: “Prior to the closure of the Ellon youth wing, the capacity of HMP Grampian was 552.
“This report suggests that the average daily inmate population is getting closer to being full.
“If the Ellon wing is not going to be reopened to young offenders, then consideration should be given to what will happen in the future.
“It could be that this additional capacity is required.
“Whatever happens, it makes little sense for this section to simply lie empty.”
SNP MSP Lewis Macdonald said: “Despite the challenges facing HMP Grampian, it is good to see that they are managing the numbers in their adult male and female population, and that the size of the prison in Peterhead is appropriate for the number of prisoners from the north-east.
“What we now need to see is these same good practices being applied to male young offenders from the north-east, who remain at Polmont in the Central Belt.
“It is high time that the Scottish Prison Service delivered the community facing prison we were promised, housing all the male and female prisoners and young offenders from the north-east under one roof.”
An SPS spokeswoman said the figures did not reflect daily changes to the population.
She said: “In terms of the capacity at Grampian, we measure capacity across all of our prison estate rather than by individual establishment.
“With regard to young offender numbers this has significantly decreased in recent years.
“Polmont, as the single establishment for the management of male young offenders has the breadth, capacity and resources to meet the aggregated needs for young offenders.
“There are various reasons why young men may be held at Grampian at any given time including being lodged for court.”