The review was dubbed a "whitewash" by Cr Christie. He said an independent inquiry was needed after Mr Watson raised serious issues in an affidavit he swore.
Mr Watson alleged Mr Simpson was prepared to unleash "skeletons in the closet" after his decision-making over the sacking was scrutinised.
In the affidavit, Mr Watson alleges that Mr Simpson stated he would respond if action was taken against him.
"He told me there were many skeletons in the closet and 'the door hasn't even been opened yet'," the affidavit states.
The affidavit also names a person whom Mr Watson alleges Mr Simpson had indicated was connected to unauthorised spending of council funds that was, in Mr Simpson's view, in the public interest.
When asked for comment, Mr Simpson told the Northern Advocate he was aware allegations had been made against him under the Protected Disclosures Act (PDA). He had not seen the allegations and declined to comment.
But Mr Christie said the affidavit raised issues that needed to be looked at, saying they highlighted the inadequacies of the first inquiry.
"The inquiry should have as broad a scope as possible to incorporate the issues in the latest affidavit, as well as what was raised prior to the elections and anything else that may arise from the matter," he said.
Cr Christie said it was important that the public had faith that the council was always acting according to the rules and in the best interests of the district.
"The affidavit raises some serious allegations and now they have come out they have to be looked into and an independent inquiry is the only way to give the public that satisfaction," he said.
"I want the public to know that we are not sitting on our hands doing nothing and we are taking the matters seriously."