The State Services Commission should apologise and compensate Derek Leask, who it criticised in a report into leaks he was not responsible for, the Ombudsman has ruled.
Former Ministry of Foreign Affairs and Trade senior advisor Mr Leask complained to the Ombudsman's office over how the State Services Commission handled an inquiry, led by Paula Rebstock, into leaks in 2012.
The 18-month inquiry, over leaks to then-Labour foreign affairs spokesman Phil Goff on the restructuring of MFAT, singled out Mr Leask and colleague Nigel Fyfe and said they had opposed the restructure.
It said Mr Leask and Mr Fyfe had lobbied chief executives of other agencies, including then-Department of Prime Minister and Cabinet chief executive Maarten Wevers.
Neither man was named in the report, but they were identifiable.
Both Mr Fyfe and Mr Leask disputed the findings and criticised the investigation. Mr Fyfe said at the time he "at no point" leaked any material and always acted within the State Sector Code of Conduct.
The Ombudsman has ruled the finding was outside the inquiry's terms of reference and that Mr Leask was not responsible for the leaks.
Ombudsman Ron Paterson recommended the commission offer a public apology Mr Leask, reimburse him for actual and reasonable expenses, compensate him for harm to reputation and review its guidance for any similar future inquiries.
Mr Paterson did not say how much that compensation should be.
He said issues of excess of jurisdiction, insufficient notice about the scope of the interviews and the lack of information about relevant standards all pointed to a lack of fairness by the inquiry and led him to conclude that Mr Leask was not treated fairly, in accordance with the principles of natural justice.
Mr Leask said it had been a long fight, but it was worth it.
"I had no objection to the thought that they were going to bring in an outside person but if they were going to do that then they need to be very sure that that investigation is going to be conducted in a proper way."
"The 2013 findings against me and against other MFAT staff have been rubbished. It is good to have the slur on my reputation removed. Today's findings by the Ombudsman go beyond the vindication of my actions."
"It essentially argued that we had been in breach of public service standards and this inquiry by the Ombudsman has demonstrated that this is simply not the case, that the evidence is not there for that finding."
He said he was also accused of not listening to the instructions of his chief executive and this was not true.
"The Ombudsman's report suggests that the 2012/13 SSC investigation was out of control from start to finish."
He said he had confidence the government and the public service would quickly act on the recommendations.
The inquiry and legal defence cost over $510,000. Mr Goff criticised the inquiry when it was announced, saying it would be a "collossal waste of time".
Ms Rebstock, a former chair of the Commerce Commission, has carried out many reviews in the public sector including of state care for children.