In its annual report, released on Wednesday, the ICAC says it received an internal complaint in the year to June 30 involving an allegation that a "Commission officer had threatened physical harm to another staff member".

The commission suspended the officer during its investigation into the incident and subsequently found the officer had engaged in misconduct.

The officer was "reprimanded, directed to apologise to the other staff member and directed to undertake counselling", the commission said in its report.

Former Supreme Court judge David Levine, QC, the Inspector of the ICAC, was "kept informed about the matter and the conclusion reached by the commission", it said.

This was the only complaint against a commission officer that was received by the ICAC in the past year, compared with three in the previous year and two the year before that.

The work of the commission has grown since its historic inquiry into a coal licence granted over a farm owned by the family of corrupt former Labor minister Eddie Obeid. Public hearings in that inquiry started in late 2012 and a final report was delivered on July 31 last year.

In the past year, the commission also concluded inquiries into a coal licence granted to Doyles Creek Mining, a company then chaired by former union boss John Maitland, and the Obeid family's interest in cafe leases at Circular Quay.

In addition, the ICAC has held public hearings in its inquiries into Obeid-linked company Australian Water Holdings and Liberal Party fundraising, which triggered the resignation of a string of government MPs.

The commission said it employed around 126 full-time equivalent staff in the past year and received 3386 "matters". This included 1043 complaints from members of the public, a 14 per cent increase on the previous year, and 674 reports from public sector agencies.

It handed down 12 investigation reports, double the number in the previous year, and conducted nine public inquiries over 84 days.

The watchdog was granted 33 search warrants in the past year, 21 phone tap warrants and four surveillance device warrants. It conducted 203 secret interviews over 97 days.

Commissioner Megan Latham said in a foreword to the report that the ICAC "has continued to cement its place as a leading integrity body in Australia".

"Now in its 25th year of operations, the Commission and the role it fulfils in NSW have not diminished; in fact, today the Commission and its work are as relevant as ever, demonstrated in the pivotal role it plays in investigating and exposing corrupt conduct at all levels of the state's public sector."

As a result of the nine public inquiries held in the past year, 41 people were found to have engaged in corrupt conduct and the ICAC recommended the Director of Public Prosecutions consider criminal charges against 39 of them.