Harrison, citing calculations from international maritime unions watching the Auckland port project because of its unique operation of automated and manual systems at the same time, believes the cost of the project is $500 million to $600m.
New Zealand port sector watchers put the cost, so far, at north of $400m.
The port and its owner Auckland Council have refused repeated Herald requests to state the cost to date.
The port company, in written responses to some of Harrison's claims, said the union, here and in Australia, "is ideologically opposed to automation and is hell bent on undermining efforts to automate in both countries".
It noted the maritime union in Australia had recently launched a campaign of industrial action at an automated terminal in Melbourne "causing disruption to the supply chain in Australia which will have flow-on consequences for New Zealand".
"That they have done this during the Covid pandemic shows the reality of how little concern the Maritime Union has for disruption in the wider community."
Harrison, who said he was a stevedore at Ports of Auckland for 23 years "so pretty much knows how it works down there", said the union did not want to stop automation.
"It'd be good if it worked properly. But no port in the world is trying to do what Auckland port is."
Sector critics claim the unfinished automation project meant the port was not prepared when Covid-19 disrupted global shipping schedules, causing congestion at international ports and Auckland as shipping lines responded to severely reduced air freight space and a spike in consumer demand for goods.
The port company did not respond to the Herald's request for figures for crane and container hourly moves this year. The union claims they are well below industry and international standards.
Pressed to respond to specific union claims, including software linking problems and the prospect that with winter coming the final terminal civil works still needing to be done could take months, the port company in a statement said the union "continued to make wild claims about automation that frankly don't deserve an answer".
"The automation project is delayed because of Covid, not because of any inherent fault with the system.
"We are part-way through implementation. The system is not yet finished or fully optimised, so of course it is not yet performing to its full potential.
"Performance is improving as we get to use and test the system more frequently and it will continue to improve."
The port has blamed a stevedore labour shortage for part of its ship unloading and loading delay problems and has enlisted Government help to fast track the entry of five overseas crane drivers. It is trying to recruit more workers in response to the congestion problem.
The union's Harrison said more labour is needed because productivity has dipped. He claims there were present and past staff with stevedoring and crane driving experience who could have been enlisted on fixed contracts to help ease the congestion.
They had been moved aside or dispensed with because of the port company's "overconfidence" in the automation system, he said. The union represents 164 of the port's estimated 220 stevedores.
Final container terminal civil works to allow full implementation of automation were due to start next month, but have been delayed until April, with provisos, to give freight operations priority. The port company this week said an April start was still the plan.
Maersk, the world's biggest container shipping line, has told the Herald port congestion is expected to continue until at least June when the export season peak is over.
Maersk has withdrawn 50 per cent of its Auckland call service because of the port's congestion.
Harrison suggested that if Ports of Auckland could not increase its productivity, its dividend returns to Auckland ratepayers may have to be generated by an increase in port charges on users.
