Ports of Auckland is making its striking workers redundant and will contract the work out.
In an announcement this morning it said it was moving to a "competitive stevedoring model" for unloading cargo.
It said workers would be given the chance to apply for jobs under the new regime.
Ports chief executive Tony Gibson acknowledged the decision would have an impact on staff and their families.
"This decision has not been made lightly, but we believe it is vital to ensuring a successful and sustainable future for the port, including protecting jobs over the long term," he said.
Maritime Union national president Garry Parsloe said workers were gutted by the move. "Port management wants to take away job security from 300 ordinary working families.
"There is no basis for this proposal. We're already providing flexibility and have offered even more in negotiations with the Ports.
Mr Parsloe said the announcement "flies in the face of public opinion". He urged Mayor Len Brown not to let it happen.
"His legacy cannot be that he stood by while these workers were treated in this way."
Mr Parsloe said workers do not accept their jobs should be casualised.
"We cannot let Ports of Auckland get away with this move. This is by no means the end of our campaign for secure work," he said.
Mr Brown said he was disappointed with both Ports of Auckland and the Maritime Union for not coming to a resolution. He was concerned at the disruption the industrial dispute was causing at the port. However, legislation prevented him from intervening to resolve the dispute, he said.
"I am on only one side in this dispute. The people of Auckland. We deserve a port that is competitive, a decent return for rate payers and a settlement that is sustainable.
"My powers to intervene in this dispute are severely limited by legislation surrounding the port. However the people of Auckland can be confident that I am in constant contact with both parties in the dispute and they are aware of my concerns about the consequences for Auckland as a whole and the families directly involved."
Ports of Auckland said the decision to introduce "competitive stevedoring "was partly the result of the impact of long running industrial action on its business.
Mr Gibson said 292 employees, mainly stevedores, would be affected by the move.
Redundancies would begin later next week, with striking staff encouraged to apply for new positions, he said.
"This decision has not been made lightly, but we believe it is vital to ensuring a successful and sustainable future for the Port, including protecting jobs over the long term," he said.
Ports of Auckland chairman Richard Pearson said the company's priority was to win back lost business.
"This decision will reassure the wider market and customers that we plan to achieve a sustainable lift in the port's competitiveness as soon as possible.
"We have our sights set high. Our ultimate goal is to become not just New Zealand's most efficient and productive container port, but a leader in the Asia Pacific region."
Labour Party employment relations spokeswoman Darien Fenton said it was an "absolute certainty" the redundancy decision would leave families in poverty.
Today's decision also raised questions about whether Ports of Auckland was negotiating in good faith with the Maritime Union.
"There has been evidence of a desire to have [the Maritime Union] out of Ports of Auckland and this is one way to do it.
"When you're allegedly negotiating in good faith and at the same time going through the process of contracting out, that raises questions. I understand that's a matter for the courts and there will be some questions around that."
Solidarity in the south
Meanwhile, Christchurch port workers are planning strike action in a solidarity move with their Auckland comrades.
Unionised workers at Lyttelton Port are planning to boycott work on a docked ship but the move could be blocked by an emergency court hearing this morning.
Lyttelton Port of Christchurch chief executive Peter Davie told Radio New Zealand this morning that he understood more than 300 Maritime Union members were refusing to unload the container ship, Lisa Schulte, as it had been worked on by non-union staff at the Port of Auckland.
Mr Davie said: ``We had discussions with unions ... about that and what action they may or may not take.
``We have to find a way through.''
Mr Davie said he considered the action illegal and had already filed an Employment Court injunction to force staff back to work, following similar measures taken by port companies in Wellington and Tauranga.
The case was due to be heard in Christchurch today ahead of the ship's scheduled arrival at Lyttelton at 7.30pm this evening.
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