Ms Bain, who blamed the Post Office for failures that led to victims being prosecuted, appeared before MSPs to answer questions over the scandal in Scotland.

“The wrongly accused and convicted sub postmasters and postmistresses are due an apology from those who have failed them, and I do that today as head of the system of criminal prosecution in Scotland,” she said.

She added: “Where miscarriages of justice have happened, it is because prosecutors in Scotland accepted, as they were entitled to, evidence and explanations at face value from the Post Office.”

The Post Office gave the Crown Office assurances in 2013 that the Horizon IT system was not defective but “prosecutors took the decision to take no further prosecutorial action in several newly reported cases” in September of that year.

In October 2015 Post Office officials met again with prosecutors in Scotland but had failed to provide an expert report supporting the integrity of Horizon.

Ms Bain said: “On 22 October 2015, prosecutors were advised to assess all Post Office cases and report for Crown Counsel’s instruction with a recommendation to discontinue or take no action in cases which relied on evidence from the Horizon system to prove a crime had been committed.”

She also noted that “not every case involving Horizon evidence will be a miscarriage of justice”, stressing the importance of going through the “established route of appeal” through the Scottish Criminal Cases Review Commission and Appeal Court of the High Court of Justiciary.