A third of prisoners at Low Moss jail are still living in "sub-standard" dormitories which were first used as a World War Two RAF camp, a report found.
The prison can house up to 330 inmates
The concern was raised by the Chief Inspector of Prisons, Dr Andrew McLellan, after a follow-up inspection.
But he said the conversion of six other dormitories into cells had improved life at Low Moss, north of Glasgow.
Living conditions at the jail, where up to 27 short-term prisoners share single large rooms, are unique in Scotland.
Dr McLellan said the refurbishment of six dormitories had created "very good" accommodation for about two thirds of prisoners at the prison.
"These improvements are not just superficial - there has been a reduction in violence at the prison, which traditionally had to deal with considerable levels of disorder and concerted indiscipline," he said.
"Levels of anxiety and depression have dropped and there were also indications that staff were determined to make the best of Low Moss, despite the imminent prospect of closure.
"Against this very positive background it has to be remembered that more than one third of prisoners still live in sub-standard, open dormitories."
The report found that two groups of prisoners thought that life had improved at Low Moss, but a third group - which contained inmates from the five unconverted dormitories - was "much more angry and uncomfortable".
Dr McLellan said the inspection, which focussed on conditions and on the way prisoners are treated, had found a "persistent problem" over the availability of adequate clean clothes.
"Prisoners have almost no opportunity to wear their own clothing.
"Worse still, it is not easy to have clean underwear each day," he said.
He also found that very few prisoners had training opportunities and said more needed to be done to give them the chance of finding employment on release.
The report said there had been "significant progress" in tackling levels of violence and bullying at the jail.
It also identified improvements in dealing with addiction problems and said PE facilities had improved.
A spokesman for the Scottish Prison Service (SPS) said the concerns raised about laundry services had been rectified.
"There has been a welcome reduction in violence and we are pleased with the way staff are managing that.
"They are aware of the closure plans but are still keeping it running in a good fashion," he said.
East Dunbartonshire Council is considering the SPS plans for a new permanent prison.
The proposals include the redevelopment of the existing prison site, plus adjoining vacant and derelict land.
Low Moss, near Bishopbriggs, can hold up to 330 medium to low security prisoners serving sentences of four years or less.