Former sub-postmasters have called for a police investigation following a BBC report that the Post Office knew about the flaws in Horizon IT system, but continued to argue against sub-postmasters in the court.
A draft report accessed by the BBC shows that in 2017 the Post Office was shown evidence that losses could be due to errors in the Horizon software. The findings were discussed with Post Office management and investigators at the time.
However, the Post Office continued to defend the costly case with £100m of public money.
The draft report was compiled by the accountancy firm Deloitte, but it was not disclosed in court.
Labour MP Kevan Jones, who advises ministers on Post Office compensation, said the Post Office used public money against innocent people.
He told BBC Radio that the police should start their investigations. "Unless people are brought before a court of law and asked what they knew and why they took such actions, then that won't be justice," added.
The Post Office has so far refused to comment.
Horizon software manufacturer Fujitsu Group said it was fully cooperating with the public inquiry.
More than 900 sub-postmasters were wrongly prosecuted between 1999 and 2015 due to supposed losses shown by the faulty Horizon IT system.
Between 2018 and 2019, the Post Office was taken to court by 555 sub-postmasters and successfully established their innocence.
The Rishi Sunak government recently introduced a bill in parliament that will overturn convictions that were handed down in connection with Post Office business.
Damian Talbot