Auckland mayor Wayne Brown has admitted he's not sure he has the voting numbers to back his idea to sell Ports of Auckland.

Brown revealed through his 10-year plan he intends to sell the Port of Auckland’s operating business and put the proceeds into a new $3 billion-to-$4b investment fund to relieve homeowners from another heavy rates rise.

The two proposals are key planks of Brown’s 10-year budget, along with cost-cutting measures to take the sharp edges off an earlier projection from officers for a 14 per cent rates rise next year.

Brown will propose a rates rise of 7.5 per cent for households when he releases his Mayoral Proposal next week - the first step in a lengthy process of developing the 10-year budget, otherwise known as the Long-Term Plan (LTP).

Talking to the Mike Hosking Breakfast, Brown revealed he'd learned the previous mayor, Phil Goff had already carried out secret discussions over the possibility of selling the ports.

"So I thought I'd follow that along," he said.

"We're in dire straits. We've got two big assets that are poor performers financially, I thought if we can convert that into something that will perform well then we can take that pressure off ratepayers."

Brown also noted that in a natural disaster such as a volcanic eruption or earthquake, Auckland's key assets would all be damaged and of little value for revenue - so the idea made a lot of sense.

"But do I have the numbers? I'm not quite sure."

Hosking mentioned Brown's previous attempt to raise significant funds for the council by selling its Auckland Airport shares. He only managed to walk away with half the outcome he planned.

Brown said his plan for the ports would be a repeat of the airport exercise and the outcome would largely determine what the next rise in rates would be. But support would not be easy to come by.

He said he would go ahead with “what makes the most economic sense”, even if he was unable to achieve 100 per cent of what he wanted.

"The bad news falls back on the ratepayer.”

The mayor noted some of his councillors had "a long career saying 'no' to things" but argued fixing issues isn't possible by doing nothing. He stressed he's determined to lift the burden ratepayers are experiencing.

"We've also got some big bills coming from the City Rail Link and stuff," said Brown, who thinks the rail link will be "wonderful" for the city once it's implemented.

"But like all wonderful things you've got to pay for them."

It’s well known that DP World, based in Dubai and which operates terminals in 40 countries, made an unsolicited offer to the council in early 2021 to buy the port outright or the “opco/propco” model for a long-term lease to operate the business with the land remaining in public ownership.

At the time, the council hired Melbourne-based consultants Flagstaff Partners to look at options for a possible sale. Flagstaff was also hired to provide advice on this year’s sale of airport shares.

DP World is not saying anything about its interest in the port and the Herald understands Port of Singapore, Patrick Terminals in Australia, and another big international player, Terminal Investments Ltd, are also keeping an eye on a possible sale.