Rockhampton, Queensland, Mayor Margaret Strelow has resigned after being found guilty of misconduct by the Councillor Conduct Tribunal though she disputes the findings.
Cr Strelow made the announcement on social media saying it took place at 5pm Monday.
"After months of silence the Councillor Conduct Tribunal has decided that I am guilty of misconduct," Cr Strelow said.
"I absolutely refute their finding."
The findings were in relation to a day trip to one of Adani's solar farms.
Cr Strelow said she acted at all times in accordance with her conscience and on the advice of senior legal practitioners as well as on the advice of officers from the Department of Local Government.
"(It was) part of an official visit and normal day to day work for a Mayor (with) itinerary drawn up by the Premier and my participation approved by full Council," she said.
"My refusal to agree that I may have been compromised in some way by the visit is a matter of personal integrity for me. And I cannot with a clear conscience agree that a reasonable person would believe I might have been."
According to new laws the mayoral position will now pass to Chris Hooper the only other candidate in March's election who only got 30% of the vote, compared to Cr Strelow's 70%.
The laws state that a sitting mayor or councillor would be replaced by the next highest polling candidate if they were to die or resign in the first 12 months of their term
"I wish to apologise to my community who may now have a Mayor who was not of your choosing. I remain hopeful that the government will find a way to allow you to have a by-election," she said.
"Right up until the decision today I could not believe that a fair and independent tribunal could possibly find as they have done.
"I am leaving this community in better shape - financially and in outlook than when I returned to office in 2012."
Cr Strelow has been mayor of Rockhampton for 16 and a half years with three years before that as Councillor.