The Public Service Association claims the "vital data collection and analysis" relied on by government and businesses is at risk as job cuts loom at Stats NZ.
A PSA spokesperson said Stats NZ unveiled plans to save $2.4 million by reducing its workforce.
In the proposed cuts 39 workers will be made redundant before Christmas.
Public Service Association national secretary Kerry Davis said it feared the changes would rob Stats NZ of experienced subject matter experts, data analysts and there would be fewer managers to lead teams and manage workloads.
"Statistics claims this is all about removing duplication. We say it should consider shifting resource to where the pressure points are in the organisation rather than risk losing experienced people.
"The PSA will be making a strong case to stop these decisions as it supports those who may lose their jobs and those who are facing an unrealistic increase in their workloads."
Impacted staff have just seven working days to provide feedback on the plans.
PSA assistant national secretary Fleur Fitzsimons was concerned more job losses could be coming for the Stats NZ workforce.
"We stand opposed to these cuts and the unrealistic short consultation period," she said.
"They will put at risk vital data collection and analysis which is relied on by other parts of government, business and communities all over New Zealand.
"All New Zealanders depend in some way on the decisions made by government, businesses and other organisations based on quality and trusted data. It's important to help inform a multitude of government decisions that are all about improving the health and well-being of communities across Aotearoa.
"We don't believe Statistics NZ's proposal aligns with its purpose as stated in its latest annual report. The importance of high quality, trusted statistics and data cannot be overstated. Together, they form the foundations of an open and well-functioning democracy, supporting good government and public confidence."
Fitzsimons said the cuts would create anxiety for "scores" of workers and their whānau within mere weeks of Christmas.
A spokesperson for Stats NZ said it would release a statement when information was available.