Industrial action on Auckland's waterfront is spreading to Christchurch with workers at the Lyttelton port planning to refuse to work on a container ship.
In a show of support for their northern counterparts, hundreds of Maritime Union members will on Wednesday boycott a ship that has been handled by non-union labour at Ports of Auckland.
Radio New Zealand understands from speaking to several union members that the watersiders will ban work on the container ship Lisa Schulte when it arrives from Auckland on Wednesday afternoon
Lyttelton Port of Christchurch chief executive Peter Davie says he hopes there will be no action, and is meeting union members during the morning to discuss the issue.
Mr Davie says if any action is taken, he will seek an Employment Court injunction - as port companies in Wellington and Tauranga did - to force staff back to work.
More than 300 members of the Maritime Union are in the second of four weeks of strike action weeks as they try to negotiate a new collective agreement with the port company.
The president of the International Transport Workers' Federation, Paddy Crumlin, who is based in Australia, says dispute has drawn negative attention internationally.
Mr Crumlin told Morning Report that Ports of Auckland has been declared a 'port of convenience' which in union terms identifies it as one of the worst ports in the world for industrial relations and employer behaviour.
"If shipping companies want to go there, it has ramifications with dockworkers and seafarers aboard their ship and dockworkers at other ports they go to."