Over a hundred people look set to lose their jobs at Transfield, the company that manages Chorus' fibre and copper network.
Staff found out about the company's restructure and the proposal to cut 137 jobs across the country, via video briefing last week.
The Engineering, Printing and Manufacturing Union (EPMU) said 80 percent of workers would also be paid a base salary, much lower than their current rate, which would be topped up according to the number the jobs they did.
EPMU telecommunications spokesperson Joe Gallagher said skilled workers were being unfairly treated.
"It's really quite heartbreaking to see and we will lose all these guys with critical knowledge of our local networks because they'll just walk away and get jobs somewhere else."
Mr Gallagher said the workers were paying the price for Chorus' mismanagement of the Ultra-Fast Broadband project.
Transfield said the changes were necessary to remain competitive.