Just over half of corruption complaints lodged in relation to Australian Federal Police members are not being resolved within benchmark times.
The Commonwealth Ombudsman found in a report tabled in federal parliament 49.5 per cent of complaints were resolved within the benchmark, and in two categories of complaints the rate was 20 per cent.
"Resolving complaints in a timely manner is vital in ensuring the effectiveness of a complaint management system, raising conduct and practices issues for resolution, and building public trust," the report said.
The AFP's own service charter states a commitment to "fair, and where possible, timely complaints resolution and adherence to laws and standards which govern the handling of complaints".
"There is a risk the AFP's persistent low adherence to timeliness benchmarks for resolving complaints may undermine this commitment," the ombudsman said.
Complaints from members of the public and AFP appointees range from discourtesy and customer service to allegations of criminal conduct and corruption.
Timeliness has been an issue since the ombudsman's first review of the AFP complaints system in 2007/08.
The AFP's complaints management team told the ombudsman it had recently formalised the practice of allocating complaints investigations to managers.
While this had extended the time taken to handle complaints "investigations were more thorough and comprehensive as a result", the ombudsman was told.
A second issue adding to the delay related to a new national guideline that complaints be subject to a "natural justice loop" where the team provides seven days for the subject of a complaint to respond to the investigation findings.
The ombudsman identified instances where conflict of interest declarations were missing, not signed, or not dated at the beginning of an investigation in 17 per cent of formally managed complaints reviewed.
In one case, the conflict of interest declaration was signed more than two and a half years after an investigator was assigned.
And in another, investigators were instructed to backdate declarations to the start of the probe.
The ombudsman also recommended better training for staff involved in administering and investigating sexual harassment and abuse allegations.
The AFP advised a new complaints management model was due to be launched this year.