Former Post Office boss Paula Vennells has quit boardroom positions at retailers Morrisons and Dunelm as well as her role as a Church of England minister after a major miscarriage of justice.
It comes after 39 sub-postmasters had their wrongful convictions for theft, fraud and false accounting overturned on Friday by the Court of Appeal.
Ms Vennells was chief executive of the Post Office from 2012 to 2019 when reports of a faulty IT system called Horizon were not properly investigated.
That led to a vast miscarriage of justice in which hundreds of postmasters, many of whom have already won a civil case against the Post Office, were prosecuted.
On Monday, supermarket chain Morrisons and homeware retailer Dunelm confirmed, as first reported by Sky News, that Ms Vennells was to depart as a director of their boards with immediate effect.
Morrrisons chairman Andrew Higginson said: "Paula has been an insightful, effective and hardworking non-executive director, and, on behalf of the board, I want to thank her for her significant contribution over the last five years."
Dunelm chairman Andy Harrison said: "We respect Paula’s decision to step down from the board and I would like to thank her for the positive contribution she has made to the business since her appointment in September 2019."
Ms Vennells said in a statement on Friday said she was "truly sorry" for the suffering caused to sub-postmasters and committed to cooperating with an ongoing government inquiry.
She also announced, on Sunday, that she would be stepping back from her duties as an associate Church of England minister in Bromham, Oakley and Stagsden, in Bedfordshire.
"It is obvious that my involvement with the Post Office has become a distraction from the good work undertaken in the Diocese of St Albans and in the parishes I serve," Ms Vennells said
"I have therefore stepped back with immediate effect from regular parish ministry."
The diocese said she had informed the Bishop of St Albans, the Rt Rev Alan Smith, who is the son of a former postmaster.
Those wrongly convicted in the Horizon scandal have fought for years to clear their names.
One of them, Seema Misra, was pregnant when she was wrongly sent to prison after being accused of stealing £75,000 from her branch.
Helen Pitcher, chairman of the Criminal Cases Review Commission (CCRC), which referred the sub-postmasters’ convictions to the Court of Appeal, said: "This has been a serious miscarriage of justice which has had a devastating impact on these victims and their families.
"Every single one of these convictions has clearly had a profound and life-changing impact for those involved."
Appeal court judges said on Friday that the state-owned Post Office knew there were issues about the reliability of Horizon yet continued to insist it was "robust and reliable" and "effectively steamrolled over any sub-postmaster who sought to challenge its accuracy".
"Post Office Limited’s failures of investigation and disclosure were so egregious as to make the prosecution of any of the ‘Horizon cases’ an affront to the conscience of the court," the judges said.