About 130 workers at Custom Coaches, Villawood have been told the company will be closing its facility.
The Australian Manufacturing Workers Union (AMWU) NSW state secretary Tim Ayres said the union had been warning the state government for months that the jobs of worker at the facility were in a perilous position if Gladys Berejikilian did not act to offer bus building contracts to NSW suppliers.
Mr Ayres slammed the inertia of the NSW Government.
"This facility has been closed by Gladys Berejiklian and Mike Baird," he said.
"Every manufacturing job lost is a family and community tragedy.
"These 130 tragedies could have been avoided if the state government was willing to get off their hands and fight for local jobs."
Tim Ayres will be holding a press conference at the site at 2.30pm.