AMWU assistant state secretary Craig Kelly says the federal and state governments are to blame for the job losses.
He said Keppel Prince encountered planning restrictions on wind tower construction, and said it recently tendered for the Webb Dock redevelopment but that was awarded to a South Korean company.
Mr Kelly said the federal government's move to lower the renewable energy target was also a factor.
"The domino effect of that has been felt very swiftly at Portland, in Denis Napthine's electorate," Mr Kelly said.
"I haven't heard the state government screaming from the rooftop about the Renewable Energy Target and the direct impact on a very large engineering company in Portland.
"I think the new Commonwealth government has been a very large contributor with the uncertainty that they've put in the business community around the Renewable Energy Target."
Premier Denis Napthine blamed the wind energy industry, saying it was a disgrace they were using imported wind towers rather than locally produced ones at Keppel Prince.
"They ought to hang their heads in shame for importing towers and costing local jobs," he told reporters.