Prime Minister Justin Trudeau's carbon tax is the "single biggest issue killing jobs," Ontario Premier Doug Ford claimed Wednesday, blaming it for the looming closure of the General Motors plant in Oshawa.

"You could be for manufacturing jobs or you could be for the carbon tax, but you can't be for both," Ford told reporters following an emergency meeting with his cabinet at Queen's Park.

"Scrap your job-killing carbon tax plan," he said, addressing the prime minister.

After manufacturing cars and trucks for more than a century, Oshawa will find itself without an assembly plant next year.

The sudden decision is part of GM's pushes to streamline its global operations and focus on developing electric autonomous vehicles with higher profit margins elsewhere.

While Canadian engineers will get a piece of that research and development, Oshawa assembly workers will not. The Detroit-based automotive giant has said it's looking to hire more Canadian engineers to help develop the company's software for these kinds of vehicles and that the Oshawa plant isn't set up to build them.

Meanwhile, GM is also making cuts to four facilities in the U.S. — two assembly plants in Michigan and Ohio, and two propulsion plants in Michigan and Baltimore — all of which aren't subject to the same carbon emission regulations as Canada.

Watch Premier Doug Ford accuse politicians and the union of "selling false hope":

Ontario Premier Doug Ford accused Prime Minister Justin Trudeau of "grandstanding" and "selling false hope and empty promises" to autoworkers facing a layoff in Oshawa. 2:31

GM's announcement sent shockwaves through the town of Oshawa as more than 2,500 autoworkers face the prospect of unemployment.

Politicians at all levels of government, and all political stripes, were caught completely off-guard by GM's decision. Ford and federal Innovation Minister Navdeep Bains both said they asked GM what could be done to save the plant, only to be told the decision was final.

Trudeau has vowed the federal government will do what it can to help workers "get back on their feet." Earlier today, he defended Ottawa's carbon pricing plan as a job creator.

"The best way to secure jobs for the future is to take genuine action on climate change and help our economy and our families to thrive through the transition to a lower carbon economy," he said during question period.

"The members opposite have no plan and instead just try to play politics."

GM workers picket at an entrance to the assembly plant in Oshawa, Ont. (Carlos Osorio/Reuters)

Unifor, the country's largest private sector union, which represents the plant workers, also said it will "fight like hell" to keep the plant open beyond 2019.

"All we hear are a bunch of powerful people grandstanding, deflecting and selling false hope," Ford said, referring to the response from politicians and the union.

He added: "My promise to the workers and the families is this: We're going to fight for you like you've never seen before."

Union fires back

Jerry Dias, president of Unifor, fired back at Ford on social media, asking why the premier is "so determined to wave the white flag" at GM's plan.

"The only empty promises are the ones that [Ford] made to the workers of Ontario," Dias tweeted.

Dias says Canada can't afford to sit idle as the GM shifts vehicle production to low-wage jurisdictions like Mexico. (Carlos Osorio/Reuters)

He also took issue with the premier's claim that the union's focus should be on securing other employment for the impacted GM workers.

"Find new jobs? Seriously? Is this the best that [Ford] can do?" Dias said on Twitter.

Instead, he wants GM to shift production of another vehicle to Oshawa to stave off the closure of its plant there.

David Paterson, GM's vice-president for corporate and environmental affairs, has said the facility won't be rejigged because the company has enough under-used factories elsewhere.

Why is the Ontario government so determined to wave the white flag <a href="https://twitter.com/GMcanada?ref_src=twsrc%5Etfw">@GMcanada</a>? The only empty promises are the ones that <a href="https://twitter.com/fordnation?ref_src=twsrc%5Etfw">@fordnation</a> made to the workers of Ontario. <a href="https://twitter.com/hashtag/OshawaMadeGM?src=hash&ref_src=twsrc%5Etfw">#OshawaMadeGM</a> <a href="https://t.co/chV3M5WoET">https://t.co/chV3M5WoET</a> <a href="https://t.co/VVw9QnsH8t">pic.twitter.com/VVw9QnsH8t</a> —@JerryPDias

'GM didn't make this decision overnight'

While some of those Oshawa jobs may be transferred to other Canadian plants, the impact of the job losses will be significant in Oshawa and reverberate through the surrounding regions east of Toronto as well as through the wider Canadian economy.

Ford said he wants to ensure the affected workers can find new jobs, which is why he's asking Trudeau to preserve work in the automotive industry by cutting the federally imposed carbon tax.

Cars have been built in Oshawa, Ont., for more than 100 years — a tradition that is now in doubt. (Norm Betts/Bloomberg)

It was a keystone promise of Ford's election platform, "Plan for the People," to axe Ontario's cap-and-trade, a system he has characterized as nothing more than "government cash grabs that do nothing for the environment."

The Progressive Conservative government quickly rescinded the previous provincial Liberal government's regulation that established the cap-and-trade program in 2017, withdrawing from an arrangement with Quebec and California that set up a joint carbon market and forced large companies to buy allowances for their carbon emissions.

"GM didn't make this decision overnight, they didn't make it six months ago. It is the result of years of governments that just don't care about job creators or how hard it is to run a business or create a job," Ford said.

"The sad truth is that the loss of the GM facility was 15 years in the making."

(CBC)

In that time, approximately 300,000 manufacturing jobs were lost and numerous companies moved their operations out of Ontario, Ford said.

The Oshawa facility was once one of the biggest auto assembly plants in the world. In its heyday during the 1980s, the plant produced almost a million cars a year and employed about 23,000 people.

However, this was synonymous with a larger trend in manufacturing that saw auto output flatten and shrink as car production moved to lower-cost centres and Canadian plants build more trucks and crossover vehicles.

Manufacturing now accounts for just 11.7 per cent of Ontario GDP, according to the latest provincial statistics. Before the 2008-09 recession, that figure was 16 per cent.

Trudeau must take 'immediate action'

Ford also implied that the beginnings of GM's move came about on former premier Kathleen Wynne's watch, suggesting that if he'd held the province's top job, his policies, such as lowering taxes and hydro rates, would have reined in the closure and "made it attractive" for GM to stay in Oshawa.

"If I'd been here for five years, they probably wouldn't have left," he said.

While Ontario still has a role to play as a link on the North American automotive supply chain, Ford warned other companies may soon make similar decisions if Trudeau doesn't take "immediate action" by cutting the federal carbon tax.

Ford's pitch comes a day before the PCs are expected to reveal Ontario's new climate change plan, and ahead of a first ministers meeting next week In Montreal where premiers will sit down with Trudeau.

"I'll be his champion if he drops the carbon tax," Ford said of the prime minister.

Carbon tax not linked to job loss, NDP says

Official Opposition Leader Andrea Horwath says fuelling job creation and securing company investment in Ontario isn't as clear cut as rethinking Canada's climate change action.

Earlier Wednesday, she told MPs in the legislature that she's disappointed with how the PCs have reacted to the looming autoworker layoffs, and highlighted the significance of GM's reasoning for the Oshawa plant closure.

"General Motors says their global restructuring is driven by their plans to get into the car markets of the future," she said of sagging demand for products and shifts in zero-emission technology.

Ontario NDP Leader Andrea Horwath criticized Ford's demands, suggesting the PC government doesn't appreciate the importance of protecting the future of the auto sector as it explores clean energy alternatives. (Chris Young/Canadian Press)

GM has indicated it will stop making a number of car models entirely, primarily gas-powered sedans that are no longer selling much and aren't very profitable when they do.

It's part of a push by GM to invest in areas it thinks can make more money — electric and autonomous vehicles.

GM's vice-president for corporate and environmental affairs has told CBC News that shuttering the century-old Oshawa plant will allow them to free up more resources for jobs in software development and high-tech work in Canada. The company is currently hiring 1,000 technical engineers.

"It's an industry they intend to talk to Ontario about," Horwath said.