The imports log jam due to ship unloading delays at the Port of Auckland is expected to worsen and unlikely to clear before the second quarter of next year, says Maersk, the world's biggest container shipping line.
Maersk also expects New Zealand's export season to be "challenging" because of consequent delays in the imports-for-exports container exchange on ships heading back overseas.
Maersk's head of Oceania Export Market, My Therese Blank, said Maersk ships are waiting 10 days to be unloaded at Auckland's port.
She expects the current level of congestion issues to continue at least into the new year.
Even with ships diverting to other North Island ports such as Port of Tauranga to avoid Auckland, most containers have to come back to Auckland for goods distribution and are building up in the supply chain along the way.
"We see further challenges in the supply chain."
Frustrated importers missing out on sales and Christmas orders have called on shipping lines to send more vessels but that would not solve the problem, she said. Incoming containers had to be unloaded and exchanged for exports.
New Zealand's main export port, Tauranga, is trying to handle big volumes of unexpected, diverted import shipments in its peak export season.
Shipping lines have imposed "Auckland congestion charges" of up to US$500 a container on imports. They say this is to cover extra expenses incurred by delays, redistribution of cargoes and diversion sailing costs. Importers have little choice but to pass the charges on.
Blank attributed the problem to a "labour shortage" at Auckland's port, New Zealand's main import port and owned by Auckland Council. It coincided with a surge in demand for imported goods from Kiwis unable to travel overseas and with extra money in their pockets.
The port has eight container cranes but is only operating three during the day and two at night, citing a shortage of stevedores. It started a major container terminal automation project five years ago, the cost of which is being kept secret by the port company and the council for "commercial reasons".
The company says Covid disrupted completion of automation, scheduled for early this year. It will not now be fully implemented until the end of March. In the meantime, the port is operating a split terminal, part manual and part automated, which it says affects staffing and productivity.
Meanwhile, Maritime Union Australia has blasted as "fabrication" Auckland port's statement that industrial action by its members is partly to blame for the problem because ships are arriving late from across the Tasman.
The union's assistant national secretary Warren Smith said the action ceased more than a month ago. He blamed international shipping companies for cancelling services when Covid-19 emerged. They were now imposing congestion charges as a result of "their own actions".
"Everyone in the supply chain is being told we're to blame and it's just lies. Ships are being unloaded seamlessly (here) and rail is operating seamlessly as far as I can see," said Smith.
Maersk's Blank said her company had not cancelled services to New Zealand as a result of Covid.
Smith said "lies about us are peddled every day" for political reasons.
"Ports of Auckland is playing a political game blaming Maritime Union Australia for their own inefficiencies.
"I have people ringing me chasing their widgets and saying they understand it's because we are on strike. It's simply not true."
Auckland Mayor Phil Goff told the Herald he'd been advised by port chief executive Tony Gibson there was an estimated 12 week backlog at Brisbane, Sydney and Melbourne ports which had affected services coming to New Zealand.
Goff said he had raised the congestion issue at Auckland port with Gibson, who responded that there were multiple causes affecting a range of ports around the world, including Sydney and Singapore.
The causes included Covid disruption to international supply chains and the port's automation project, industrial action in Australia which by August had resulted in 70 per cent of ships arriving late in Auckland, and the port's labour issue.
"I appreciate the problem that this is causing to consumers and businesses. Under the Ports Companies Act, shareholders cannot interfere in operation matters but I expect POAL (the port company) to take all necessary action to address the issues of congestion as quickly as possible."