Mayoral runner-up Reynold Macpherson has taken legal action of last month's election results.

Rotorua's local government election was "rigged" in favour of incumbent Mayor Steve Chadwick.

That's the bombshell claim made by Mayoral runner-up Reynold Macpherson, who has launched legal action to get the election results declared null and void and a new election held.

"A re-election is a real possibility," he said.

BENN BATHGATE/FAIRFAX NZ Council chief executive Geoff Williams and Rotorua Mayor Steve Chadwick.

"The evidence suggests to me the election was rigged."

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Citing the Local Electoral Act 2001, Macpherson has filed a petition at Rotorua District Court claiming the decision by Rotorua Lakes Council chief executive Geoff Williams to delay release of the National Research Bureau (NRB) community satisfaction survey until after the election, and the running of 'advertorials', were examples of bias by Williams that unfairly affected the election results.

CHRISTEL YARDLEY/FAIRFAX NZ Rotorua mayor Steve Chadwick wouldn't comment on the legal action given it was now before the court.

"It is with the utmost reluctance that I have taken this possibly unprecedented step," he said.

"In this case I believe Mr Williams has fallen short of his duty and has unfairly influenced the outcome of the election."

The annual NRB survey is usually released in June or August, but Williams previously said this year's release was delayed until the end of October to enable further analysis of the results, a claim rejected by Macpherson.

"The CE [chief executive] responded by claiming that the CSS 2016 [Consumer Satisfaction Survey] report lacked clarity and required additional comparative analysis of the demographics and 'quite a lot of close scrutiny'. There was no report of the outcomes of this additional analysis in the Annual Report."

Macpherson said the Act allowed a two week period for a Judge to examine his claims, then a further two weeks for evidence to be called.

"Pretty soon after that the Judge can make a decision on paper or call for hearings," he said.

"There's every reason logically to be confident because of the evidence and the letter of the Act."

As well as influencing the mayoral election results, Macpherson claimed Williams exerted undue influence on the election of council members too.

"His actions during the recent election were biased in favour of the incumbent mayor and her power bloc of councillors and were unfair on the other candidates. They materially affected the outcome of the election by enabling a significant number of the incumbent councillors to be re-elected by slim margins."

"As chief executive of the Rotorua District Council, Mr Williams was in a unique position to influence the outcome of the election."

Rotorua Mayor Steve Chadwick declined to comment as the matter was now before the courts, while Williams issued a brief statement.

"We will await the outcome of the process," he said.