Scotland’s prisons are “bursting at the seams” as new figures show the majority were at, or over, capacity last month.
HMP Barlinnie in Glasgow was operating at 139% capacity in December while HMP Inverness was at 137%.
Scottish Liberal Democrats’ justice spokesman Liam McArthur warned that inmates were being “packed into prisons like sardines”.
The Scottish government said it was focused on stopping people going to prison in the first place.
The figures were revealed following a parliamentary question from the Lib Dems.
Other sites at, or exceeding, their prisoner limit were Addiewell, Dumfries, Edinburgh, Glenochil, Kilmarnock, Perth and Shotts.
Five prisons out of 15 were at, or beyond, their capacity at the start of 2018 – the figure rose to nine by the end of the year.
Those operating within their capacity last month were Cornton Vale, Grampian, Greenock, Low Moss, Polmont and Castle Huntly.
Mr McArthur said: “These new figures show that our prisons are bursting at the seams with the majority now full or overcrowded. People are being packed in like sardines.
“Those working in prisons have warned that the population surge is putting services at risk and jeopardising progress.
“Prison capacities are set for a reason. Staff need to work in a safe environment.
“Overcrowding makes it harder for them to work with individuals and help rehabilitate them.”
‘Urgently ease pressure’
Mr McArthur also criticised short-term sentences, saying evidence showed they were less effective at rehabilitation than “robust” community-based sentences, which would reduce the pressure on jails.
He added: “That is why the Scottish government now must get on and introduce a presumption against short-term sentences of less than 12 months.
“Ministers need to urgently ease the pressure on our prison system and change the way we deal with less serious offenders to make our communities safer.”
A Scottish government spokesman said: “Scotland has the highest rate of incarceration per 100,000 of population of any Western European country, which is why we are focused on action to stop people going to prison in the first place.
“Our approach to reducing reoffending has seen reoffending rates drop to a 19-year low, and we are committed this year to extending the presumption against short prison sentences in favour of more effective community penalties.”