The closure of Oshawa’s GM plant will immediately result in the loss of a combined 4,400 jobs on the assembly line and at parts manufacturers across Ontario and the job loss will only grow over time, a union-commissioned study has found.

The study was conducted by Robin Somerville, who is the president of Quantitative Economic Decisions Inc.

It found that if General Motors follows through with their plans to close the Oshawa plant in 2020, it will result in the immediate loss of 4,400 jobs at the facility and manufactures which serve it. The study said that job loss will then rise to an average of 6,300 over the next five years.

The study also says that there may be as many as 14,000 fewer jobs across the province by 2025 due to an estimated $4 billion annual reduction in Ontario’s GDP.

While the study does concede that there could be a slight uptick in employment across Canada at first as laid off workers move to other parts of the country it estimates that 10,000 jobs will eventually be lost outside Ontario due to a weaker economy.

Provincial government revenue would also fall by $330 million in 2020 and an estimated $500 million a year by 2030 while federal government revenue would drop by $520 million a year, according to the study.

"There would be a major ripple effect that would be felt far beyond Oshawa and even Ontario," Unifor President Jerry Dias said in a press release. "We're asking Canadians and governments at all levels to make it clear to GM that we will hold them accountable should they decide to inflict this damage by closing a top-quality and productive plant for no other reason than corporate greed."

The release of the study comes one day after Dias met with GM officials in Detroit to make his case for extending the life of the Oshawa plant, though he came away from that meeting empty handed and told reporters that the auto manufacturer was guilty of “corporate greed” and was “picking a fight with all of Canada.”

GM has, for its part, has said that the closure of the plant is necessary as it shifts its focus to electric and autonomous vehicles.

On Tuesday, GM Canada’s Vice president of Corporate Affairs David Paterson told The Canadian Press that the union should work with the automaker to help retrain the estimated 2,600 employees that will be impacted by the plant closure and transition them to new opportunities.

According to the study, there were 159,000 vehicles produced at the plant in 2017 accounting for about $680 million of Canada’s GDP.