Workers claim mental health support will be reduced under proposed changes to a compensation scheme, labelling it a Labor government "betrayal".
The NSW government said it was "modernising" its beleaguered workers' compensation scheme, with physical injuries still treated in the same manner as psychological ones.
But unions say the cost-cutting measure will add financial and legal barriers to accessing assistance.
Such is their anger, Unions NSW has launched a rare advertising blitz targeting the state's Labor government, backed by the Australian Workers Union.
"These changes will make it harder for seriously injured workers to access long-term critical care for their mental health," AWU state secretary Tony Callinan told AAP.
He pointed to a requirement that workers claiming vicarious trauma prove a close connection to someone involved in a workplace death or serious injury before accessing support.
That change was not revealed during government consultation with unions, Mr Callinan said.
National park employees finding people who took their own lives, as well as transport workers cleaning up highways after serious car crashes would have claims knocked back because they didn't witness the incident, he said.
He conceded the current scheme needed reform but cast the proposed changes as against Labor values.
"People with true Labor values don't disadvantage workers," Mr Callinan said.
"It is a betrayal of AWU members who have been campaigning tirelessly for first-responder recognition.
"The NSW government finally recognised these workers just last month, and now want to strip away their workers comp to try and fix their leaking budget."
Unions NSW secretary Mark Morey said workers with psychological injuries would be forced to court before accessing compensation.
"Whether it's a hospital worker or prison officer with PTSD, a child protection worker who has had to remove a child from an abusive home, or a shop assistant abused at a checkout, these workers deserve support when workplace trauma catches up with them," he said.
Treasurer Daniel Mookhey's office has been contacted for comment.
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