A call has been made for hundreds of Post Office staff wrongly accused of theft and false accounting to all have their convictions overturned.

More than 700 Post Office managers were convicted when faulty accounting software made it look as though money was missing from their sites.

A board overseeing compensation said until all convictions were quashed, “we cannot put the scandal behind us”.

The Ministry of Justice said it would respond in due course.

The Post Office Horizon scandal – named after the faulty accounting software – constitutes Britain’s most widespread miscarriage of justice.

The convictions of hundreds of postmasters and postmistresses for false accounting and theft between 2000 and 2014 resulted in some people going to prison.

Many were financially ruined after being prosecuted and some of those wrongly accused have since died.

Wendy Cousins was convicted of theft in 2009. She had pleaded guilty, but her son Paul told the BBC’s Today programme that she had only done so in order to avoid a prison sentence, as she thought she would not survive going to jail.

She took her case to the Court of Appeal in 2021 but the judges refused to overturn her conviction, saying it was not based on Horizon evidence. She died last year.

Paul said anger was the overriding emotion he felt about the fact his mother died with her conviction still hanging over her, as well as “sadness and frustration, bitterness and everything else that comes with it”.

He said the call to overturn all the Post Office convictions was “massive news”.

“Of course it’s great news for everyone,” he said, but added for him it did not go far enough, as he would like to receive an apology and to see the people who prosecuted his mother go through what his family had been through.

In September, the government said Post Office staff who have had wrongful convictions for theft and false accounting overturned would be offered £600,000 each in compensation.

But so far, only 93 convictions have been overturned, according to the Horizon Compensation Advisory Board, an independent group overseeing compensation related to the scandal.

Prof Chris Hodges, chair of the board, said they believed more than 900 postmasters had been prosecuted in relation to the faulty Horizon software.

He said while individuals could apply to have their convictions overturned, the small number of cases meant the “current approach is not working”.

The reasons for this, Prof Hodges added, included an unwillingness of people to appeal due to a “deep distrust of authority”, evidence being lost or destroyed, and issues with compensation if a Post Office manager is not granted a retrial.

“The convictions are unsafe not only because they relied on the Horizon computer evidence, but also because of egregious systemic Post Office behaviour in interviews and pursuing prosecutions,” he said.

“This led to guilty pleas and false confessions, driven by legal advice to victims to minimise sentences, and by the psychological pressure of dealing with an institution systematically disregarding the truth and fairness.”

Prof Hodges said the “only viable approach” was for “all 900+ Post Office-driven convictions from the Horizon period” to be overturned.

“A small minority of these people were doubtless genuinely guilty of something. However, we believe it would be worth acquitting a few guilty people (who have already been punished) in order to deliver justice to the majority – which would not otherwise happen,” he said.

Criminal barrister Flora Page represented three clients who successfully appealed against their convictions.

“At the time that the Court of Appeal heard both Wendy Cousins’ case and also my original three clients’ case, they didn’t yet know about the widespread endemic problems in the prosecutorial set-up at the Post Office,” she said.

“And so they drew a very clear distinction between those cases which clearly involved the Horizon system and those cases which maybe had some other evidence, such as a confession.”

She said she hoped the recommendation to acquit everyone would be significant, but fears it may be difficult to deliver, particularly as the courts have already refused a number of appeals, such as Mrs Cousins’.

“And legislation overturning a court decision is something which most people would feel was constitutionally uncomfortable,” she said.

A Post Office spokesperson said: “We strongly encourage people who believe they were wrongly convicted, for any reason, to consider an appeal.”

The Ministry of Justice said it recognised the “hardships that postmasters and their families have had to endure and are seeking to right the wrongs of the past”.

“To date over £130m has been paid in compensation and we are introducing new legislation to ensure all those affected by the IT scandal do not miss out,” a spokesperson said.

“We want the criminal appeals system to be as efficient and effective as possible which is why we’ve asked the Law Commission to examine whether reforms are needed. We look forward to their findings once the review has concluded.”