"The congestion has meant that there are significant delays getting product on to [the] shelf, and that freight costs have increased substantially. Retailers urgently need to see more capacity come onstream at Ports of Auckland, and Retail NZ is calling for the Government to expedite the arrival of trained crane operators and port workers from overseas if necessary."
Maersk's Blank also warned industrial action at Australian container terminals was a concern for New Zealand supply chains, resulting in delays to ship arrival times. There was a four-day strike at Sydney in January and strike action was due to start at a Melbourne terminal on February 16, she said.
Cargoes that would have been loaded or unloaded at Auckland are being handled through Port of Tauranga and its Auckland inland port MetroPort.
Blank said shipping congestion was a growing issue and now affected South Island ports.
It was impacting both importers and exporters and moving perishable goods in a timely way was becoming a challenge. New Zealand's primary sector peak export season will ease off by June.
Even with the removal of 50 per cent of Maersk's Auckland port calls there was still a delay of 12 to 14 days before ships could be unloaded at Auckland, she said.
"Until Auckland improves its rate of productivity we would not want to revert back to our standard number of port calls."
The Auckland Council-owned port was the country's main marine import gateway prior to late last year.
On the brighter side, Blank said Maersk was introducing a new international service soon connecting New Zealand with Fiji, Suva and Lautoka.
The new service, Sirius Star, will have a rotation of Suva, Lautoka, Tauranga, Auckland, Nelson, Timaru, Lyttelton, Nelson, Timaru, Lyttelton, Tauranga, Suva.
Blank said in addition to accommodating "world-to/from-Fiji" cargo, the new service would improve flexibility dealing with another New Zealand supply chain headache - getting a logjam of empty containers from Auckland and Tauranga to the South Island exporters needing them.
The Sirius service, when coupled with a change to Maersk's Southern Star service, would improve transit times from New Zealand to international markets by up to 10 days, she said.
Meanwhile, Blank said it was "very positive" Auckland port had announced it had secured a new crane operator.
"That's when we will see the difference when they can operate an additional crane."
Ports of Auckland blames a labour shortage for worsening a congestion problem which originated from Covid-19 disruption to international container shipping. It has been seeking to recruit five crane operators from overseas as part of a drive to find more than 50 stevedores.
A port spokesman said progress was good.
"We are getting good support from Government officials which is making the process smoother."
But he could not say when the first overseas candidate might arrive in New Zealand as there were "still too many unknowns at this stage".
The port has eight ship-to-shore cranes but is only using three during the day and two at night because of the labour shortage. But sector critics believe a big part of the port's productivity issue is its terminal automation project, started in 2016 and yet to be fully implemented.
The final stage of automation implementation - terminal pavement work - was due for completion at the end of March but has been delayed again due to freight taking priority.
Container ships wanting to unload at Auckland have been forced to wait at sea for up to 10 days since October last year.
Blank said Maersk was being asked why it doesn't just acquire land to ease the container jam problem but logistics systems were complex and couldn't be popped up overnight.
She warned industrial action at Australian container ports was concerning for New Zealand supply chains as it delayed ship arrival times.
In Sydney there was a four-day strike in January and more industrial action was due to start on February 16 at one of Melbourne's three container terminals.
"Ships will arrive late into New Zealand ports, not only at Auckland but other ports around New Zealand. It is becoming an issue with South Island port congestion now."
Rising shipping costs are a big concern of New Zealand importers and exporters, with some saying they have doubled and trebled in the past year. Some shipping lines have also imposed Auckland congestion charges on import containers.
Blank couldn't discuss whether shipping charges were likely to keep rising because of a market information blackout with Maersk posting its latest annual financial results this week.