In February and March more than 300 prisoners, half of them serving sentences for violent offences, were released early after prison chiefs warned they could take no more arrivals. At that point, the prison population stood at 8,326.

Seven months on, it has climbed to 8,359. A Scottish government forecast suggests the figure could rise to 8,750 by the end of the year.

The Scottish Prison Service (SPS) said the increase was destabilising jails and urged action to reduce numbers. The Scottish government said it was working with the SPS to manage the prison population sustainably and noted that an independent review of sentencing is due by year’s end.

The rise has been attributed to a backlog of people awaiting trial and a sharp increase in sexual offences cases.

Those released in February and March were serving sentences of under four years and had completed at least 40 per cent of their term. Offenders convicted of domestic abuse or sexual crimes were excluded. A similar initiative in 2024 saw 477 short-term prisoners released after serving half their sentences.

Scotland’s prison population peaked in 2012 at 8,420. SPS chief executive Teresa Medhurst has previously warned it is a “realistic expectation” that this record will be surpassed.

The system’s designed capacity is 7,805, but it has been running above that level for some time. In July, officials projected that the average daily population in December could be as low as 7,950 or as high as 8,750 depending on court schedules.

The pressure is acute, with ten of Scotland’s 17 prisons now rated at red risk status – up from eight in June – meaning they are struggling to cope with current demand.

An SPS spokesperson said: “We have been managing an extremely high and complex population for more than a year and the number of people in custody set to rise even further.

“This has an increasingly destabilising effect on our establishments, with staff unable to do the critical work of building relationships and supporting rehabilitation, and prisoners frustrated by the impact on their daily lives and the opportunities available to them.”

Speaking last month, Justice Secretary Angela Constance said: “There is no single reason for the increase and there is no single solution,” she said.

“We have taken a range of actions to address this, including changing the point of release for some short-term prisoners and bringing forward regulations to widen the use of home detention curfew, which enables selected individuals to be released to serve the last part of their sentence under curfew and clear licence conditions.”