Some of the male inmates were appearing in courts in Glasgow and Airdrie when they were let out by G4S staff in error. The details have been revealed in figures from the Scottish Prison Service showing prisoner movements from April to September last year. The Prison Escort Statistics show seven prisoners were "unlawfully at large".
An SPS spokeswoman said two were "released in error" in the Strathclyde Police area. They were let out by G4S after their first court appearance - despite having other matters to answer to.
The first was released from Airdrie Sheriff Court last May and the second from Glasgow Sheriff Court in June. The SPS, G4S and Strathclyde Police could not confirm if they were still free.
But Labour MSP Graeme Pearson, inset, a police officer for 38 years and the ex-director general of the Scottish Crime and Drugs Enforcement Agency, blamed the mistakes on the "incompetence in the administration and management of prisoners".
He said millions of pounds of public money would be saved if prisoners appeared in court via video link instead of being transported to court for short appearances.
He said: "There could be seven people in a cell in court. The name of a person who is to be given bail is called and the wrong person steps forward and is let out, duping the officers. The risk would be significantly reduced if prisoners could appear via video link"
Mr Pearson said five prisons have the technology for video link appearances, including Barlinnie, Glasgow, and Low Moss, Bishopbriggs.
He added: "The annual bill for G4S is about £20million. If we were able to do 20% of appearances via video link the financial impact would be substantial."
A G4S spokesman said: "Following these incidents, which are rare, steps [were] taken to minimise the risk of them happening again."
A spokesman for SPS said that of the seven prisoners who were, "unlawfully at large," six were released from court, and one escaped G4S custody but was recaptured soon after by police.