Tens of thousands of auto workers could be out of work if the General Motors plants in Oshawa shut their doors, a new study suggests.

The study was conducted by the Centre for Spatial Economics on behalf of Unifor, a union that represents workers at both assembly plants.

The Centre for Spatial Economics found that closing the plants would result in a loss of 33,000 jobs in a period of two years. The move would also cut more than $5 billion from Ontario's gross domestic product and cost the Ontario and Canadian governments $1 billion in lost revenue, researchers said.

There are approximately 4,000 workers in the complex in Oshawa, but the study said each of those jobs lead to more work outside of the plant.

The research says that 10 jobs are created for every one job at the GM plants. The other jobs are created at parts plants, transportation companies and the communities where workers spend their salaries.

One of the two GM plants in Oshawa is slated to close next year.

The future of the other plant is unclear. It was announced in 2012 that the Chevrolet Camaro production line would be moving from Ontario to Lansing, Mich. by 2016.

GM has not moved production of any other vehicles to the Oshawa plant to replace the Camaro line.

The union wants the federal and provincial government to step in and make sure the plant stays open.

"Today is really about a call to action. We can't delay the decisions," Unifor National President Jerry Dias said at a news conference Monday.

"We need to be aggressive and we need to go after future investment and I'm optimistic that we can do this."

Jim Stanford, Unifor chief economist, said the report showed that keeping the plant open was not a "question of charity," but a potential hit to federal and provincial revenue.

"This is clearly a question of government making an investment to make sure that that continuing flow of revenue remains there."

CTV Toronto's Paul Bliss reported that the Ontario Liberal government is happy with the report, saying it reinforced the positive impact of the government bailout of GM in 2009. Ontario Minister for Economic Development Brad Duguid said he's optimistic that GM will stay in Oshawa even after the Camaro line winds down.