Lord Advocate Dorothy Bain is coming under pressure to explain why the Crown Office and Procurator Fiscal Service (COPFS) took sub-postmasters in Scotland to court despite knowing there were problems with the Horizon IT software.

On Wednesday, the Crown Office said they had been made aware of problems with the evidence supplied by the Post Office in May 2013, but did not stop prosecutions until 2015.

The scandal of the faulty software which made it look as if hundreds of owner-operators in charge of sub-post offices had stolen money, dominated Thursday’s First Minister’s Question.

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Anas Sarwar used his time at the session to highlight the case of Peter Worsfold, a sub-postmaster in Inverness between 1997 and 2002, who told the public inquiry of how Post Office employees came to his door “with menace” to demand money they wrongly believed they were due.

Mr Sarwar said it was “behaviour reminiscent of the mob.”

“These stories show that the Post Office behaved like a private police force and showed little regard for the law in Scotland.

“Sub-postmasters were pressured into accepting accusations of false accounting and forced to hand over thousands of pounds that day or face imprisonment.

“If any other organisation had behaved like this in Scotland we would expect to see criminal investigations into their conduct.”

The First Minister said he empathised in the "strongest way possible with the harrowing tales that we’ve heard from subpostmasters and subpostmistresses right up and down the country.”

He said the actions of the Post Office should be “interrogated” and said it is for the Crown Office to consider allegations of criminality.

Unlike, in England where the Post Office’s Security and Investigation team pursued private prosecutions against sub-postmasters, it was the COPFS who ultimately went after those accused of stealing in Scotland.

The Crown Office estimates that up to 100 people in Scotland have been convicted due to the faulty Fujitsu software.

So far, only 16 Scots have asked the Scottish Criminal Cases Review Commission to look at their convictions.

It was confirmed on Thursday afternoon that two of them - Judith Smith and Colin Smith - have had their convictions overturned.

That brings the total number north of the border to four.

During First Minister’s Questions, Douglas Ross shared comments from Stuart Munro, convener of the Law Society of Scotland’s criminal law committee, who said this week that the Procurator Fiscal should have gone public when they first learned of the problems with Horizon.

The Scottish Conservative leader said the Crown Office had serious questions to answer.

“The Crown Office in Scotland must be transparent – prosecutors were aware of issues with the flawed Horizon system more than 10 years ago, so First Minister, we don’t need meetings or briefings from the Lord Advocate, we need her here in Parliament to answer questions about this scandal," he said.

Responding, Mr Yousaf told MSPs that Scottish prosecutors were told in September 2013 not to use evidence which relied on Horizon to treat cases reported by the Post Office.

“Then, of course, no cases were prosecuted from 2015 where the sufficiency of evidence was dependent on the evidence from the Horizon system.”

He said the Crown Office had been assured by the Post Office that Horizon had no bearing on live Scottish cases between 2013 and 2015.

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Rishi Sunak announced on Wednesday that the UK Government would bring in new legislation to quash the convictions of those convicted in England and Wales.

Mr Yousaf promised that the Scottish Government would do similar in Scotland.

He said ministers would either use a legislative consent motion to effectively allow the UK Government to legislate in a devolved area or would develop separate legislation to deliver the same effect for Scotland.

Some of the victims of the scandal died before they could clear their names, and it has been linked to four suicides.

There has been a groundswell of public anger in recent days thanks to the ITV drama, Mr Bates Vs the Post Office, based on the stories of some of those wrongly pursued.