Shipping lines are reported to be cutting services to New Zealand which could means goods wanted for Christmas may not make it.
The Customs Brokers and Freight Forwarders Federation said demand for space on ships is up a quarter on a year ago, which is expected to increase in the run up to Christmas.
"There has been a worldwide surge in consumer demand. Shipping companies did not anticipate this and significantly restricted capacity due to the fall in demand when China effectively shut down due to Covid-19," its chief executive Rosemarie Dawson said.
"Lines are now at capacity, so it is very difficult to get space on ships coming out of China."
Dawson said some shipping lines had begun bypassing New Zealand to reduce delays in their own schedules, with no plans to add extra services.
"These factors, taken together, are leading to an increase in spot market rates - which are used to set pricing for shipping freight.
"We expect these will continue to increase from this point."
The situation was not helped by industrial action in Australia, which had created disruptions for vessels leaving Sydney for New Zealand, she said.
"Importers should provide as much lead time as possible for bookings - ideally more than three weeks in advance of sailings."