Mr Brown was questioned about providing a reference for Ms Chuang for a job she applied for and got at the council-run Auckland Art Gallery.
"I did not abuse my position of power, there will be many, many people around Auckland who have received similar letters of recommendation,'' he said.
"At that point in time, this was very very early in the relationship that I had with her so I wrote, as I do for many people across Auckland, and that is just a normal letter of support and reflection of what I knew of her at that time.''
Mr Brown spoke at length about the effect of the relationship on his family.
"Life is not without regret and you make decisions and when you make a stupid decision like I did you have to live with that and try to find a way to move forward.''It's been pretty devastating on the family but I'm loved by my wife and my children in particular and we are just working this out,'' he said.
John Hawkens protested outside the event, yelling "Shame on you'' and "What you did has sullied the name of Auckland''.
Mr Brown poked fun at himself at the opening of the show home, by commenting on the photo-voltaic power generated on the roof for water heating.
"I'm in a bit of hot water at the moment,'' he said.
Meanwhile, the scope of the independent review ordered by Auckland Council chief executive Doug McKay into the use of council resources during the affair has been revealed.
Ernst and Young will examine the following:
* Any use of council resources within the Office of the Mayor, in respect of the Mayor's relationship with Ms Chuang, that contravenes council policies (eg payments and procurement).
* Any improper preferential treatment in relation to Ms Chuang's engagement as an employee, contractor or an advisor within the Auckland Council Group.
* Any other issues that the reviewers or chief executive considers relate to, or arise out of, the above matters.
The review will cover the period between November 1, 2010 and 21 October, 2013.
The findings will be reported back to the chief executive as quickly as possible, in no more than four calendar weeks.
The review has the support of the mayoral office which will cooperate fully with it, a council spokesman says.
Mr McKay said it was important that the public had full confidence in the council's processes and that all expenditure and activity was open to public scrutiny.
Last week Mr McKay confirmed he was not aware of any specific information or anything contrary to the Mayor's assurances in public and to him in person.
The review is not specific to the elected members' code of conduct but will cover council policies and procedures and will provide background information should any code of conduct review be initiated.
Auckland Council and Ernst and Young said they will not make any public comment on the substance or progress of the review until its findings are released.