A report into the pair's affair, released this afternoon, said Mr Brown used his council phone to make 1373 calls and texts to Ms Chuang between November 19, 2010 and October 21, 2013.
Ms Chuang said all of the calls and texts were of a personal nature.
The mayor also received nine free hotel rooms which he didn't declare, valued at $6130.
He also failed to declare 54 hotel upgrades valued at $32,888.50.
Mr Brown made one reimbursement of $263 for personal phone use on October 2012 but no subsequent reimbursements have been made.
Mr McKay said the council was unable to quantify the amount Mr Brown would need to pay to reimburse the calls.
"There were some instances where the relevant council policies were not fully met, or the use of resources raised questions. These include the amount the mayor reimbursed to council for costs incurred for personal mobile usage,'' Mr McKay said.
The review found mayor Mr Brown didn't show any improper favourable treatment towards Ms Chuang, including the reference he provided for her job at Auckland Art Gallery.
Brown responds
Mr Brown released a statement in response to the findings of the Ernst & Young report.
He said the report confirms his assurances that he did not misuse council resources, and nor did his mistress Bevan Chuang receive preferential treatment.
"I supported the Chief Executive's decision to commission this review. I welcome the conclusions, and I believe they draw a line under the questions that the review sought to address."
Mr Brown admited he should not have accepted free rooms, and should have disclosed that he had in October.
"This was an error of judgement and I apologise to the people of Auckland," he said.
"I remain totally focused on the issues that matter most to Aucklanders, including improving our transport system, tackling Auckland's housing crisis and continuing to invest in our future."
Mr Brown said the report included details in relation to his and his family's private use of accommodation that were not within the scope of the investigation but that he needed to address.
"The report notes that over a three-year period I, and my family, stayed privately in hotels in central Auckland on a number of occasions. The arrangements for these hotels were made privately in most cases, and in all cases payment was made privately.
"My reason for staying in the central city is that I often work until late in the evening - attending meetings, functions or civic events - and I start work early the next morning, often for media interviews or breakfast events. A significant number of these rooms were also booked and used privately by me and my family.
"I was not charged for nine of these hotel rooms, including one occasion in relation to Ms Chuang."
Mr Brown said the report noted he never used council resources for private accommodation or in relation to Ms Chuang, and does not hold a council credit card.
"However, I accept that as Mayor I am subject to a higher standard of public accountability, and in this context I should not have accepted the free rooms offered to me, and should have disclosed this fact when I was asked about it in October."
Mr McKay revealed the Ernst & Young report at a media briefing earlier this afternoon.
The report had not been made available to the media before the briefing.
The review's terms of reference relate to any use of council resources in respect of Mr Brown's relationship with Ms Chuang that contravene council policy, and any improper preferential treatment given to Ms Chuang as a council employee, contractor or adviser.
It was also able to probe "any other issues that the reviewers or chief executive considers relate to, or arise out of, the above matters".
Mr Brown took legal advice on the report after being given a draft version on Friday.
Since receiving a draft copy of the report seven days ago, Mr Brown has received legal advice before providing feedback yesterday.
Mr McKay has received legal advice from Crown Solicitor Simon Moore, QC.
- by Cassandra Mason
