Scotland’s top prosecutor has been urged to appear before MSPs to answer questions on the Horizon scandal.

This week, it emerged up to 100 people had been convicted due to the faulty Post Office system Horizon in Scotland, while almost 1,000 were caught up in the scandal across the UK.

North of the border, prosecutions were dealt with by the independent Crown Office, as opposed to Post Office-led prosecutions elsewhere.

A spokesperson for the Crown Office said on Wednesday it had been made aware of problems with the Horizon software in May 2013.

But the Scottish Conservatives claimed on January 29 of that year, a prosecutor cited “issues with Horizon as reasons for not proceeding with a case” – four months before the Crown Office says it was made aware by the Post Office of issues.

Tory leader Douglas Ross raised the issue at First Minister’s Questions in Holyrood on Thursday, and called for Lord Advocate Dorothy Bain KC to appear before MSPs to answer questions about the scandal.

First Minister Humza Yousaf told MSPs the Crown Office issued guidance warning against reliance on Horizon for evidence in September 2013 and effectively stopped prosecutions in 2015.

Mr Ross said: “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.

Subpostmasters were pressured into accepting accusations of false accounting and forced to hand over thousands of pounds that day or face imprisonment

“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.”

Responding, the First Minister said he had a conversation with Ms Bain on Thursday and feels she is “willing to consider” appearing before MSPs, but he added it is for her to decide as the independent head of prosecutions in Scotland.

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.