The Post Office has said that its chief executive, Nick Read, has been cleared of any wrongdoing in an investigation after the existence of whistleblower allegations was dramatically revealed in parliament. Read has been “exonerated of all the misconduct allegations” brought by a whistleblower after an investigation by an external barrister. In a statement released on Wednesday, the Post Office also criticised its former chair, Henry Staunton, for revealing that Read was under investigation. The existence of the whistleblower allegations added to the problems at the Post Office, which is under intense scrutiny in an inquiry into the scandal over its Horizon computer system. Errors with the system led to the wrongful prosecution of hundreds of post office operators for supposedly stealing money. The inquiry is scrutinising the failings at the Post Office that led to the scandal and whether it was covered up. Rishi Sunak described the scandal as “one of the greatest miscarriages of justice in our nation’s history”, but the government has taken years to promise to quash convictions based on Horizon evidence. Staunton revealed the existence of the separate investigation into Read’s conduct in parliament in February, astonishing MPs by claiming that the Post Office’s human resources director had compiled an 80-page “speak up document”. The Post Office said that an independent barrister had examined the allegations in the complaint over the course of months. “Following several interviews and examination of documents by the barrister, Nick has been exonerated of all the misconduct allegations and has the full and united backing of the board to continue to lead the business,” the statement said. The revelation of the existence of the whistleblower complaint was “unacceptable”, the Post Office added. It said that “‘‘speak up’ allegations will always be thoroughly and consistently investigated, whoever they are aimed at”, and that it would not provide further details of the substance of the complaint. However, it appeared to acknowledge that there were problems identified during the investigation, saying that the barrister had made “recommendations on where improvements can be made to Post Office’s processes”. Staunton was removed from his post in January by the business secretary, Kemi Badenoch, after she publicly accused him of lying in saying the government had put pressure on the Post Office to slow compensation payments to post office operators. Staunton had alleged that he was the victim of a “smear campaign” after reports that he was under investigation. He claimed that the investigation into his conduct formed a small part of the much larger investigation into Read’s actions. A department for business and trade spokesperson said: “Ministers are pleased to confirm that the independent barrister has cleared the Post Office chief executive, Nick Read, of the allegations against him and he remains in post and has the confidence of the government. We feel this report has drawn a line under the issue and now regard the matter as closed, which allows us to turn our full attention to ensuring postmasters are compensated quickly and fairly.”