Inland Revenue is standing by its decision to use psychometric testing as part of a massive restructure which will see more than 800 employees re-apply for their jobs.
Staff have been told 30 percent of IRD's workforce will go by 2021 and the Public Service Association (PSA) union is fighting the use of psychometric testing in the restructure.
PSA has filed papers with the Employment Court.
It said about 800 staff reapplying for jobs were initially told they have to do psychometric tests, along with an interview and self assessments, as part of the process.
IRD has since sent out an email telling staff they can now choose whether to complete the psychometric assessments, but if they do not sit the tests, it could affect their chances of getting a job.
"The decision will [then] be based mainly on your interview, and will not include the broader picture that can be provided through the psychometric assessments.
"Given that the new roles include new skills and capabilities, this may mean that we have insufficient information that we can rely on to be satisfied of your capability to perform these new roles," the letter said.
The union's national secretary, Erin Polaczuk, said the tests were completely irrelevant, and could be used as a means to unfairly get rid of people.
"The tests themselves are incredibly subjective. And when it comes to a person's personality there is no right or wrong. We also don't think it's ethical to force somebody to undertake a test that is, essentially, a psychiatric test," she said.
"We don't know how much weight they're going to be giving these tests, and they're testing a person's personality, so if you don't want someone who asks difficult questions, or isn't compliant, maybe you would use it to get rid of particular people."
Psychometric tests are used by employers to assess people's intelligence and personality, and usually involve situational and multiple choice type questions.
Some tests try to give an insight into a person's personality type by asking how strongly they agree with statements, or by offering up hypothetical scenarios and asking respondents to prioritise them.
Ms Polaczuk said the were unnecessary.
"Many of these staff have worked with this agency for years and have undergone performance reviews and assessments over that time. Surely the details that are gained through those types of discussions and their relationships with their managers means more than this pseudo-scientific testing."
Jane Bryson, an associate professor at Victoria University's School of Management, agreed the tests should not be necessary for people already in an organisation, who management would already have ample information about.
But she said they could be a useful tool in some situations.
"For particular types of occupations a personality questionnaire may be useful.
"For instance things like sales-type jobs, some management jobs, maybe jobs where you require staff to have some good ability to cope with stress in the job."
However, Barbara Buckett, an employment law specialist with over 35 years' experience, said using them in this context was "legally dubious".
She said the tests could potentially breach the State Sector Act, which states employers must choose the most suitable candidate.
If the tests did not relate to suitability for the role, that would potentially be a breach the law, she said.
"They're dubious legally, and I think they're offensive to fair and open and transparent processes. And certainly in terms of selection processes, they're also questionable as to whether under the State Sector Act they are able to sort out the best-suited candidate for the position, which is the legal requirement," she said.
"The PSA are right to have picked this up. I think it's an issue that should be addressed. I think it's an inappropriate use of a process, and in today's world... there's issues of good faith and openness. I think they are a problem."
An IRD spokesperson said they have requested an urgent hearing in the Employment Court to resolve this matter as soon as possible.
A date for that hearing Is yet to be scheduled.