The piece, co-authored with councillor and mayoral candidate Vanessa van Uden and departing councillor Gillian Macleod, was found to breach the council's code of conduct.
It ran in the Otago Daily Times on July 26.
The article was also published by The Southland Times.
In his report to a council meeting on Wednesday, Mayor Clive Geddes found statements in the article were "defamatory of the chief executive [Debra Lawson] by implication, and the deputy chief executive [Stewart Burns] by direct reference".
It was also noted under the code council staff did not have a right of reply regarding remarks made about them by councillors.
The report also stated councillors were accused of "not having regard for due process, commercial good sense and democracy".
However, Cr Gilmour's apology was unanimously accepted by council and Mr Geddes later said he considered the matter closed.
In a letter to Mr Geddes, dated September 26, Cr Macleod defended the reasoning behind the statement.
"I believe we are all fundamentally on the side of the greater public good, but have different viewpoints; and some of us can be wrong at times.
"But this should not make us enemies. We should put aside hostility and suspicion and accept that we have a different perception of events," she wrote.
The letter also included a reply from Cr van Uden, backed by Cr Macleod, which addressed the accusation of the code of conduct breach.
Cr van Uden denied the breach was a "slight" on the judicial independence of lawyers Simpson Grierson, hired by the council to defend a High Court case brought against QLDC by Air New Zealand and the Queenstown Community Strategic Assets Group.
The issue bore no relevance to the council or the code of conduct, she said.
