Speaking to the Otago Daily Times after the meeting, Sir Tim said he would be seeking legal and governance advice as it was ''very clear'' the matter needed to be considered by an external source, shielded from political influence.
''I am forced to take the matter further so that future elected members are given basic protections from the CE's self-created ad hoc powers,'' he said.
He was hugely dismayed his fellow councillors could not put aside what he described as ''their blind loyalty'' to Hadley to look at the facts of the findings.
''I am more resolute than ever that her actions were unlawful. The review hints at this by saying council's policy and procedures were lawful but it did not have the teeth to analyse the actions of the CE.''
In August, Sir Tim told a Local Democracy reporter he believed Hadley had accessed one of his emails and used it against him at a meeting.
Hadley later issued a statement acknowledging she should not have shared the contents of the email with other elected members and staff.
However, she highlighted, that on April 27, the council passed a resolution authorising her to take the necessary steps to assist deputy mayor Nobby Clark in his support of the mayor and to represent the city.
The council decided to undertake a $10,000 review of the arrangements in place for electronic access to the mayor's email account.
In the review, Buchanan said the arrangements in place were lawful but he could not reach a conclusion if the email in question could be considered a personal communication, as the system in place did not extend to purposes of media management.
''It is clear that the arrangements and the associated systems and processes are lawful and, by and large, appropriate.
''The degree of uncertainty has made it difficult ... to say whether the established systems and processes were followed with regard to the email.''
Clark said he would oppose a further review, as it would cost more money.
Cr Rebecca Amundsen put forward a recommendation on the report which stated the chief executive's actions were appropriate, according to the findings of the report. Councillors voted in support. Sir Tim abstained.
Following the meeting, the Otago Daily Times sent questions to Hadley asking if she would do the same thing if similar situation happened in the future.
She replied the review concluded that the arrangements in supporting the mayor's email management were lawful and appropriate.