A draft report on former Auditor-General Martin Matthews should be made public, Transparency International says.
The report by the retired public servant Sir Maarten Wevers criticised Mr Matthews' performance as chief executive of the Ministry of Transport while major fraud was being committed there.
In February, Joanne Harrison was jailed for three and a half years after stealing more than $700,000 under Mr Matthews' watch.
Transparency International New Zealand director of ethics Charles Hett said the decision invited speculation and diminished transparency.
"It suggests there's something inside the report that he committee doesn't want people to read about.
"If we want to continually create an environment to prevent corruption it is a no-brainer best practice to release public reports."
He said expectations about the Auditor-General were high, and the highest levels of integrity and accountability should be expected.
"If the report indicates that ... mistakes have been made then the important thing is for us to learn from them."