The Downtown carpark and its surrounds are "one of the main redevelopment and public realm opportunities"in the council's city centre masterplan.
The masterplan says the view from the carpark in Lower Hobson St is "one of Auckland's finest, but is currently reserved for vehicles".
A council source said the carpark was one of the most strategically important sites on the waterfront.
In a statement, Mr Rowntree and Mr Brown said they were disappointed at the council's
decision to reject their offer.
The pair hoped the offer would help reduce planned rates increases and enable Queen Elizabeth Square to remain open to Aucklanders and in public ownership.
The council is currently negotiating the sale of Queen Elizabeth Square, in the heart of the CBD, with a publicly listed company.
"James and Simon are disappointed that the council has decided not to consider alternatives to privatising Queen Elizabeth Square to fast-track the Auckland City Rail Link and reduce rate increases," a spokesperson for Mr Brown and Mr Rowntree said today.
"Nevertheless, they accept the council's decision and that's where the matter will rest, enabling them to focus on other business opportunities."
Councillor Cameron Brewer congratulated Mr Town for not accepting the offer and putting commonsense ahead of an opportunistic fire sale.
"Our cash-strapped Mayor would've been very tempted just to take it and run, but the reality is if council ever decided to sell, that building and location could command much more than $75 million.
"That's what the commercial real estate and development sector are telling me.
"I think there could well be a case for the council to get out of the business of owning car parking buildings but I'm pleased we're not flogging off our best CBD parking asset to the first person who presents a cheque," Mr Brewer said.