The Labour Party says the Ports of Auckland move to contract out its workforce will do nothing to make the port more productive.
The party's economic development spokesperson, David Cunliffe, says even if the company succeeds with its plan, the economy will be worse off.
Mr Cunliffe says the Ports of Auckland's approach of outsourcing its workforce won't do anything to improve productivity at the port and would instead lead to the loss of experienced staff and undermine morale.
Business New Zealand chief executive Phil O'Reilly says Mr Cunliffe is simply making political assertions.
Mr O'Reilly says the company would have made its own assessments about the likely productivity gains from its proposal.