Auckland councillor Cameron Brewer wants a council review into Len Brown's affair with Bevan Chuang widened to investigate a trip the mayor made to Hong Kong.
Mr Brown has not officially declared the trip in January this year, sparking criticism from Mr Brewer and in right-wing circles.
The mayor travelled alone on the Hong Kong Government-funded "special visitors programme" trip to look at infrastructure projects and governance issues.
Bevan Chuang, the Hong Kong Chinese woman he had a two-year affair with, told the Herald she did not accompany him and was in New Zealand at the time.
Mr Brewer yesterday said the review had to examine the Hong Kong trip at least to assess any relevance it may or may not have to the matters under investigation.
"If the mayor is so squeaky clean, they should be encouraging Ernst & Young [the company doing the review] to investigate the trip if only to kill off the ongoing speculation once and for all," Mr Brewer said.
He said Wellington mayor Celia Wade-Brown took part in the same Hong Kong Government programme in 2012, gained approval from the council and reported back.
Mr Brown yesterday refused to say why he did not declare the Hong Kong trip in an annual return listing any third-party travel costs in the council's pecuniary interest register.
His office is shielding the mayor from media questions about the trip. It took a posting on the right-wing Whaleoil blog for the mayor's office to confirm the trip, from January 20 to January 26.
Last night, his office said the 2013 declaration had yet to be finalised and his travel to Hong Kong would appear in the 2013 declaration of interest early next year.
Council chief executive Doug McKay said he had reviewed the trip and found no evidence of any connection with Ms Chuang or any improper use of council resources.
What the rules say
Mayor and councillors must make an annual return of interests, including: "Contributions to travel costs made by third parties to a member and the value of the contribution'