Brake component manufacturer PBR says it will make 60 workers redundant as early as next week, with another 20 to follow.
And Unidrive, a company that supplies axle components to Australian car-makers and to General Motors in the United States, has said it will sack 40 workers.
Unidrive said higher steel prices, a drop in exports to the US and a drop in demand from local customers were factors that had led to the redundancies.
Australian Manufacturing Workers' Union Victorian secretary Steve Dargavel said it was vital tariff protection remained for the Australian car industry.
His call comes as the federal government considers the report on the Australian auto industry released earlier this month by former Victorian premier Steve Bracks.
The report recommended a cut in import tariffs from 10 per cent to five per cent by 2010, the manufacture of more environmentally friendly vehicles and bringing forward a $500 million federal green car fund to start next year.
Dargavel blames slow sales of locally-made cars on "years of neglect in industry and trade policy".
"We need better trade and industry policies to ensure that redundancies like these do not continue to occur," Dargavel said in a statement.
At a time when manufacturing on a global level is growing, Victoria needs to protect local industry and make sure that we re-tool for the global manufacturing sector.
"We need strong tariff protection and interventionist policy to secure the future of the manufacturing sectors in Australia."
It has been a tough year in the automotive sector, with the loss of 970 jobs when Mitsubishi closed its Adelaide assembly plant in March, followed soon after by Ford's announcement it would close its six-cylinder engine plant in Geelong by 2010, with about 600 jobs lost.
Then, last week, Ford announced it would also sack up to 350 workers as it cuts production in the face of slow large car sales.
Earlier this week, truck manufacturer Kenworth said it planned to make up to 80 workers redundant from its Melbourne factory
