Prison populations began to escalate in the 1980s and the costs of keeping prisoners in work became prohibitive.
Professor Newbold said the problem with working prisons was that they tend to be expensive to run and were seldom economically viable.
"Most prisoners are unskilled and training them can be slow and costly,'' he said.
"Expert training staff has to be employed, extra security has to be provided and the machinery and equipment needed to upskill prisoners can be expensive and require constant upgrading and maintenance.
"The products of prisoner labour cannot generally be sold on the open market because it is unfair for an unpaid labour force to compete with industries. Thus prison industries nearly always run at a loss.
"However, if a significant number of prisoners could be trained for careers, put into work after release and diverted from lives of crime, the added costs could be money well spent.''