THE chief executive of the Integrity Commission says there was a significant rise in complaints about Department of Health and Human Services last financial year.
About a quarter of those were related to conflict of interest.
Integrity Commission chief executive Diane Merryfull said she could not explain why the number of DHHS-related complaints had risen from six to 15 in a year.
"Agencies come and go in terms of the number of complaints we get about them," Ms Merryfull said.
But she said the commission's investigation into nepotism and conflict of interest by then Tasmanian Health Organisation South chief executive Jane Holden and then THO North-West chief executive Gavin Austin was one of the larger, more complex jobs they had done.
Ms Merryfull said there was one investigator employed full-time for the duration of the one-year investigation, with another full- time investigator coming in about half-way through.
She said other team members contributed on occasion, including when the commission searched three buildings used by THO-NW.
The commission served 20 notices requiring people to be interviewed, and 18 notices requiring records or information.
Ms Merryfull said Ms Holden and Mr Austin were interviewed, and both had legal representation.
"They were also given the opportunity to look at and comment on relevant parts of the draft investigator's report," she said.
Ms Merryfull said Mr Austin and Ms Holden were also able to provide a submission in response to the draft findings.
In 2013, the commission investigated other allegations of misconduct in recruitment in an area of DHHS unconnected to Ms Holden and Mr Austin.
As a result of that earlier investigation, the commission recommended that a mandated process of declaration of knowledge or association be established in state service selection processes.
The commission repeated the recommendation, among 10 others, in the report related to Ms Holden and Mr Austin.
Ms Merryfull said she could not offer more details on the earlier investigation, nor could she say whether there were any other ongoing cases involving DHHS.