Wellington City Council will progress with an investigation into Mayor Andy Foster after a councillor lodged a formal complaint about his behaviour, the Herald understands.
Before councillors voted to sell and lease council-owned land at a meeting two weeks ago, Councillor Jenny Condie revealed she had made the complaint.
Condie claims Foster showed her information the morning of the vote she believed he did not have permission to share, and was potentially defamatory to a former council officer.
"These allegations are similar to those which were heard by the High Court in 2018 and dismissed. I believe it is extremely unwise for the Mayor to attempt to unfairly besmirch the professional integrity and probity of a former Council officer," she said in her complaint.
"The actions of Mayor Foster were improper in my view and I am taking this opportunity to request that you investigate his actions. I believe that I am not the only councillor that Mayor Foster has shown this information to."
Council chief executive Barbara McKerrow later confirmed she had received the complaint and was taking advice on the matters raised.
It's now understood external independent lawyers will be appointed to investigate.
Condie declined to comment. Foster said it was "standard process" and declined to comment further.
The investigation comes after more Shelly Bay controversy erupted this week.
Foster was photographed seemingly helping a group of iwi set up tents at Shelly Bay on Sunday marking the beginning of what's expected to be a months-long land occupation.
He said the tent he was photographed with had already been erected and he was just being a "good camper" by helping out with a broken pole.
That didn't wash with many councillors, who say he has shown a total disregard for the will of the council he is supposed to be leading and has thrown them into uncharted waters.