A State Services Commission investigation due to be made public today has concluded convicted fraudster Joanne Harrison forced whistleblowers out of the Transport Ministry in 2015.

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RNZ understands the inquiry has vindicated whistleblowers who said they were forced from their jobs after they raised concerns about fake invoices Harrison was presenting and dubious travel she was taking.

Harrison stole nearly $750,000 while employed at the Transport Ministry and was sentenced this year to three and a half years in prison.

It is expected the results of inquiry will be made public later today, with the findings tipped to be highly critical of what went on at the ministry at the time.

Over five years, Harrison signed contracts with companies that didn't exist, twinked out the details of the work they supposedly did and refused to provide information about her deals to an investigation.

Two former ministry staff told RNZ they had alerted senior managers to the false invoices and dubious travel but were then targeted in a restructuring Harrison helped lead.

Others have also come forward saying they were forced out.

In March, ministry chief executive Peter Mersi refused to investigate allegations made by Labour MP Sue Moroney that members of the finance team had been unfairly restructured out by Harrison.

In May, the State Services Commission began looking into those claims, and into those of other staff who had come forward saying they felt Harrison had targetted them.

It is not clear whether any staff considered to have been forced out would get compensation.

Yesterday, Mr Mersi also admitted he was wrong to try to hide official information about the case from Ms Moroney.

State Services Commissioner Peter Hughes had issued a statement saying the ministry's conduct did not meet his expectations for how Public Service departments deal with the Official Information Act.