General Motors announced today it is shifting production of the next version of its Camaro sports car from Oshawa, Ont., to a plant in Michigan, a move that attracted sharp criticism from the Canadian Auto Workers.

CAW president Ken Lewenza called the decision a "betrayal to Canada." The Canadian Auto Workers estimates that the shift will cost about 1,000 GM workers their jobs by late 2015 or early 2016.

CAW President Ken Lewenza calls GM's decision to shift production of the Camaro from Oshawa, Ont., to Lansing, Mich., a 'betrayal.' (Aaron Vincent Elkaim/File/Canadian Press)

Taking spinoff effects at auto parts companies into account, the union says as many as 9,000 jobs in the region are at risk.

"We are outraged by this decision," Lewenza said at an afternoon news conference in Oshawa. "This is about thousands of jobs in our community."

General Motors Canada said Wednesday that "lower capital investment and improved production efficiencies were key factors" in the move — a decision it said was based on "a comprehensive business case."

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The Camaro is currently made at the Oshawa flex plant, which employs some 2,000 people and also produces the Buick Regal and, soon, the Cadillac XTS.

GM says production of the Camaro will continue in Oshawa until the end of the model cycle. But it isn't exactly clear when that will be.

GM noted that the Camaro is the only rear-wheel-drive vehicle built in Oshawa.

"Assembling the next-generation Camaro [in Lansing, Mich.] consolidates the [rear-wheel-drive] assembly with the Cadillac CTS and ATS," the company said.

GM says it recently invested $185 million in the Oshawa plant with the launch of new versions of the Cadillac XTS and Chevrolet Impala. It has also said it will add a third shift of workers to assemble the new Impala.

"Given our partnership with GM, we expected a greater level of commitment to Ontario and to Ontario autoworkers," Ontario Minister of Economic Development Brad Duguid said in a statement.

Duguid said he expects GM to "move quickly" to make good on its earlier commitments to bring new products to the facility and add a third shift on the Oshawa flex line.

NDP Finance critic Peggy Nash said Ottawa should put pressure on GM to replace the lost production in Oshawa.

"We need to make sure we're maintaining those jobs in Oshawa, that we're using our equity stake in GM to give us a voice in the future of production in Oshawa," she said.

The CAW's most recent contract with GM guarantees production of the Camaro in Oshawa only until the end of the current generation of the vehicle.

GM said it will continue to meet production targets agreed to with the federal and Ontario governments in 2009 as a condition of receiving $13.7 billion in government aid. The two levels of government together own about nine per cent of GM's common stock.

The 2009 agreement requires that 16 per cent of GM's North American production until 2016 come from Canada.