Former Commonwealth ombudsman Allan Asher has accused a Labor minister of suppressing the annual report he wrote during his last weeks in the job.
The report, which was never published, said the government underfunded the watchdog to the point it could not operate effectively.
It also warned the federal bureaucracy might be more corrupt than was commonly believed.
Mr Asher resigned in October last year in response to concerns about his impartiality, after he admitted scripting questions for a Greens senator to ask him at a Senate inquiry.
His report for 2010-11 was not tabled in Parliament, though a report by then acting ombudsman Alison Larkins was eventually tabled three months after the agency's nominal deadline.
However, Mr Asher's version can now be revealed after it was obtained under freedom of information law.
It accused the government of underfunding the ombudsman's work on immigration detention, to the point he could not be confident the public service was ''fair and accountable''.
Mr Asher also challenged the view that the bureaucracy was ''free of significant corruption''.
''Unfortunately, many of these assumptions are simply not valid, nor are they backed by substantive evidence,'' he said. ''In fact, there is little to suggest that Australian government agencies are any more immune to corruption than their state counterparts, which continue to identify and deal with systemic corruption issues.''
Ms Larkins's report omitted the criticisms.
The office of Special Minister of State Gary Gray, who oversees the ombudsman's work, said on Monday neither the minister nor his staff requested changes or delays to Mr Asher's report.
However, Mr Asher responded: ''I don't believe that for a moment.''
He said that, when he resigned, he specifically left himself enough time to finish the annual report.
''It was my intention to make these critical points on the record in such a way that, even though the current crop of parliamentarians didn't seem to have any interest in the [ombudsman's] office, there'd be a record that might be taken up in future.''
It was also ''entirely inappropriate' that another officer, Ms Larkins, tabled a report for the period he was ombudsman. ''It was done without any consultation. I didn't even receive a copy of the report.''
A spokeswoman for the current Commonwealth Ombudsman, Colin Neave, said on Monday the responsibility of clearing a public document lay with whoever held office at the time the report was presented, ''not with the person who was ombudsman during the period being reported on''.
Ms Larkins's annual report ''reflected her understanding of the work and circumstances of the office of the ombudsman''.
Allan Asher's report is available here.