Scotland’s top legal officer will appear before MSPs to face questions on the Horizon scandal, the Crown Office has announced.

Scottish Conservative leader Douglas Ross had called for Dorothy Bain KC to appear in Holyrood to clarify when the Crown knew about the flawed system which resulted in up to 100 prosecutions of subpostmasters and subpostmistresses in Scotland.

In a statement released on Thursday, the Lord Advocate was said to be finalising timings with parliamentary authorities to make a statement, after which she will take questions from MSPs.

It said: “The Lord Advocate is willing to make a statement to the Scottish Parliament on the Horizon IT prosecutions.

“She hopes to come to an agreement with parliamentary authorities about the timing of this at the earliest possible opportunity.”

The prosecution service said this week it first found out about issues with the system in May 2013.

First Minister Humza Yousaf said guidance was issued to prosecutors urging them to ensure evidence was not overly reliant on Horizon in September of that year, and prosecutions were effectively halted in 2015.

Mr Ross said during First Minister’s Questions earlier on Thursday: “There was a sudden spike in cases involving people who were some of the most trusted in their communities, but the Crown Office proceeded anyway.

“The Horizon Post Office scandal has devastated lives.

“It is the most appalling miscarriage of justice. Good people were criminalised because of an IT failure they had nothing to do with and a cover up that lasted for years – it’s right that no stone is left unturned in seeking answers.

“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.”

Mr Yousaf told MSPs: “Scottish prosecutors were told in September 2013 to treat cases reported by the Post Office in regard to the facts and circumstances and evidence which did not rely upon Horizon.

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

Mr Yousaf added that subpostmasters and subpostmistresses have “waited far too long” for justice and compensation in the scandal.

Scottish Labour leader Anas Sarwar called on the Lord Advocate to lay out a timeline of the Crown Office’s understanding, as he accused Post Office employees of acting like “the mob” by “going door to door in Scotland to threaten and extort money from subpostmasters”.

He added: “Subpostmasters were pressured into accepting accusations of false accounting and forced to hand over thousands of pounds that day or face imprisonment.”

The First Minister said: “I absolutely empathise 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 he agrees the actions of the Post Office should be “interrogated” and said it is for the Crown Office to consider allegations of criminality.

This week, the UK Government said it will look to legislate to exonerate all those impacted, with Mr Yousaf saying in a letter to the Prime Minister on Wednesday he will work with UK ministers to do the same.

At First Minister’s Questions, Mr Yousaf said the quickest way may be to extend the Westminster legislation to include Scotland using a legislative consent motion, but he added the Scottish Government will be exploring all options.

Meanwhile, a case referenced by Mr Ross where a prosecutor appeared to have knowledge of issues with Horizon in January 2013 was challenged by the Crown Office, with the spokesperson saying they had raised a “discrepancy” around dates with the public inquiry.

A spokesperson for the Scottish Government said: “The operation of the Post Office is reserved to the UK Government.

“Prosecutions and issues relating to the evidence provided by the Post Office, including concerns surrounding evidence, are a matter for the independent Crown Office and Procurator Fiscal Service.

“Given the independence of prosecutors, concerns about issues relating to the safety of evidence in criminal cases is not something the Crown Office and Procurator Fiscal Service would routinely advise ministers of.”