According to the council's Rating Information Database the capital value for Fashion Island for 2015-2016 was $11.5 million.
ACC senior media advisor Stephanie Melville said in a written statement the government department had "sold to the highest bidder with a settlement period of three and half months" and there were four bids.
During that time the purchaser found a new buyer, who had not bid in ACC's sale process, prepared to pay more, she said.
ACC was disappointed with the performance of this investment "as the annual net return of -3 per cent, per annum was below expectations".
"The main driver for low returns was the decline in demand from retailers for secondary retail locations. Our experience with this investment has informed how we would evaluate similar investments in the future."
Fashion Island, which encompasses 20 tenancies and forms part of a larger retail hub was split out from other lots and rated separately in September 2006, she said.
Labour Party spokesman Phil Twyford said ACC had "bungled here and the taxpayer as a result has taken the hit".
"It's a fire sale... it looks like they have sold it (Fashion Island) at a knockdown price."
He questioned ACC's foray into retail property which "hasn't played that well for them or the taxpayer" and "I have to say it's out of character because ACC have been a very successful fund manager of a very large amount of money".
"But if ACC is losing money for the taxpayer on deals like this the minister should be asking some hard questions about the quality of the investments and whether the right polices are in place."
In response to Labour's criticism, ACC said its overall $33 billion investment portfolio remained very strong having continued a two-decade run of outperforming market benchmarks with its investment returns.
"ACC's investment performance was laid out in annual report, which we invite you to view online."
ACC minister Nikki Kaye was not aware of the Fashion Island deal and not involved with ACC investment decisions.
She said it had a good track record of investment returns, outperforming market benchmarks consistently over the last 20 years.
"The ACC scheme's assets have grown from $10 billion in 2008/09, to $33 billion.
"The board sets the investment policy and they review it regularly. I have confidence in the board and the overall performance of their investments."
MGL Properties Ltd director Duarne Lankshear had no comment on the sale except "the new owners will be a wonderful owner and retailer for the area".
Willow Property Ltd director Peter Williams declined to comment and Opco Group Ltd director David Macfarlane cited confidentiality agreements but said in an e-mail "I believe Fashion Island will be reinvigorated in the near future which will be great for the Papamoa area".
Retail Solutions director Simon Revell said the company was the property manager for Fashion Island Ltd - which approached the developers once it knew they had bought it.
"It's no simpler than that...they (Fashion Island Ltd) tracked them down. They bought it because there is a large opportunity in the area with predicted growth."
Fashion Island would undergo an upgrade and revamp with a relaunch planned prior to Christmas, Mr Revell said. The owners were "a group of private investors that are based in Australia, they have got interests in property in Australia and various fashion businesses that includes Cotton On".
"There is going to be a marketing exercise that will be customer and community focussed. We will be working with the local community and engaging with them and getting a buy in."
The new centre would include swimwear, active wear, kids wear, menswear and youth fashion.
"Those users are confirmed and coming together with the relaunch of the centre," Mr Revell said.
