A decision document provided to RNZ showed the ministry's digital division would cut about 146 positions - including 24 already vacant - and would create about 27 new jobs.
The totals indicated a net loss of about 95 occupied roles, though some of those were filled by contractors.
The document said the cuts would save about $7.3 million a year.
Public Service Association assistant secretary Fleur Fitzsimons said the latest decision took the total job losses at the ministry to more than 700.
"This is irresponsible and unnecessary because of the extensive use of contractors in digital teams. If the ministry slightly reduced its reliance on contractors, all of these jobs could be saved."
The use of contractors was likely to increase further, she believed.
"It's very likely that if they go ahead and dismiss these workers that they will need to contract back people to do this work. The work doesn't disappear."
The ministry should have paused its decisions until the Employment Relations Authority had heard a case the union had taken against it, she said.
The union alleged the ministry had breached its collective agreement obligations by failing to do enough to find alternative positions for the staff it was laying off.
"We're asking that the ministry takes no further steps to dismiss any worker until the Employment Relations Authority considers and decides the matter.
"The breaches of the collective are serious and if the authority finds in our favour that will have a meaningful impact for individual workers."
