Efforts are being made by the Post Office to trace hundreds of people who may have been wrongfully convicted as a result of a computer scandal that caused Britain’s biggest miscarriage of justice.

Scores of sub-postmasters were prosecuted for theft, fraud and false accounting because of a faulty Horizon IT system, which led to financial shortfalls in branch accounts.

Last month, 39 former workers who were convicted and even jailed based on defective Horizon data had their convictions overturned by the Court of Appeal.

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Ex-postmistress: ‘I lost faith in justice’

In the wake of the judgment, the Post Office said it is now seeking to contact around 540 people with potentially relevant convictions and additional information is being sought in another 100 cases.

A spokesman said: “The Post Office sincerely apologises for serious historical failures. We continue to take determined action for people affected.

“Post Office has made strenuous efforts to identify individuals who were historically convicted and an extensive post-conviction disclosure exercise is taking place to identify and disclose all material which might affect the safety of those convictions.”

In its ruling last month, the Court of Appeal said the Post Office knew there were “serious issues about the reliability” of the Fujitsu-developed IT system, which was rolled out to branches in 2000, but continued to bring “serious criminal charges against the sub-postmasters on the basis of Horizon data”.

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Lord Justice Holroyde said at the time the firm “effectively steamrolled over any sub-postmaster who sought to challenge its accuracy”.

While some innocent victims of the scandal were sent to prison, others lost their livelihoods, homes and reputations.

Following the court ruling, former Post Office chief executive Paula Vennells quit as a non-executive director of high street chains Morrisons and Dunelm.

The associate minister in the Diocese of St Albans also said she would be stepping back from her regular church duties.

In an apology, Ms Vennells, who was made a CBE for “services to the Post Office and to charity”, said she was “truly sorry” for the “suffering” caused to sub-postmasters who were wrongly convicted of offences.