In mid-2020 a change was made to the Employment Relations Act 2000 to deal with what are called triangular employment relationships.
Typically these are where person A is employed by person B, and there is a contract or other arrangement between person B and person C for person A to do work for person C.
The law describes person C as a “controlling third party”.
Employees in these types of relationships can now raise personal grievances against controlling third parties and employers can join controlling third parties to personal grievance litigation.