MPs have demanded that the Treasury and other public sector organisations reveal the details of any contracts awarded to Fujitsu since 2019 as the firm continues to come under fire for its role in the Post Office scandal.
The letter to the Treasury - which was also sent to the Bank of England, the Office for Budget Responsibility and HMRC, among others - comes after the boss of Fujitsu in Europe admitted staff knew of bugs, errors and defects (BEDS) in the Horizon IT system as far back as 1999.
The spotlight is on Fujitsu following the ITV drama Mr Bates vs The Post Office, which depicted how hundreds of sub-postmasters and sub-postmistresses were wrongly held responsible for accounting errors in the faulty software developed by the international firm.
On Friday, Fujitsu executive Paul Patterson told the inquiry into the scandal, which began in 2021, that it was "shameful and appalling" that the glitches were not included in the witness statements used to prosecute hundreds of sub-postmasters over nearly two decades.
He said the "vast majority" of errors had been shared with the Post Office contemporaneously.
"There's lots of evidence of us informing the Post Office of that data that we've just discussed, bugs and errors, and how those bugs and errors did or did not impact the financial position as reported," he said.
Between 1999 and 2015, more than 700 people were prosecuted for a variety of offences including theft, fraud and false accounting - causing many to lose their jobs, livelihoods and reputations.
In 2019, the Justice For Subpostmasters Alliance - led by former sub-postmaster Alan Bates, who inspired the title of the ITV drama - won a High Court case that found "bugs, errors and defects in the Horizon system caused discrepancies in postmasters' branch accounts".
Earlier this month Rishi Sunak announced that a new law would be introduced to exonerate and compensate those caught up in the Horizon scandal and that those who were part of the group litigation order against the Post Office would also be eligible for an upfront payment of £75,000.
The scandal has prompted questions about the government's close relationship with Fujitsu after it was recently revealed Fujitsu has been awarded £6.8bn in public sector contracts since 2012 - including an extension last year to the Horizon deal.
In their letter, the MPs on the Treasury select committee ask whether the contracts went through a tendering process, whether the company's role in the scandal was considered as part of the due diligence process and whether the public sector firms have considered terminating contracts with the company at any stage.
Harriett Baldwin, chair of the Treasury Committee, said: "The public outcry regarding the Post Office sub-postmaster scandal is entirely justified, and I know I speak for the whole committee when I express my horror at the injustices the victims faced.
"It's clear that Fujitsu has questions to answer over its conduct. I think it's important we can see the extent to which taxpayer money has been spent with Fujitsu since the High Court ruling as they are simultaneously assessed on their fitness to remain a government supplier."
During his evidence to the inquiry, Mr Patterson could not say when Fujitsu became aware the Post Office was prosecuting its staff with faulty evidence.
Asked when they put two and two together, he said: "I do not believe Fujitsu knew at the time, but certainly latterly... the company became more aware that it was being used nearly solely for prosecutions."
He also said he did not know why the details of the BEDS did not find their way into witness statements, and that some references to them were edited out of evidence "by others" - something he said was "shameful, appalling".
Mr Patterson's comments today came after he faced a grilling from MPs earlier this week, in which he acknowledged his company had a "moral obligation" to compensate victims.
A spokesperson for Fujitsu said: "The current Post Office Horizon IT statutory inquiry is examining complex events stretching back over 20 years to understand who knew what, when, and what they did with that knowledge.
"The inquiry has reinforced the devastating impact on postmasters' lives and that of their families, and Fujitsu has apologised for its role in their suffering.
"Fujitsu is fully committed to supporting the Inquiry in order to understand what happened and to learn from it. Out of respect for the Inquiry process, it would be inappropriate for Fujitsu to comment further at this time."
A HM Treasury Spokesperson said: "The impact the Horizon scandal has had on the sub-postmasters and their families is utterly horrendous, and it is crucial that something like this can never happen again.
"That is why we have launched a statutory inquiry into the scandal to establish the facts of what went wrong, as well as delivering swifter access to compensation for those affected.
"We will respond to the Select Committee in due course."