General Motors is cutting 625 jobs at its assembly plant near London, Ont., as it shifts some production to Mexico.

Mike Van Boekel, spokesman for Unifor Local 88, says the layoffs will take effect in July at the CAMI Assembly plant in Ingersoll, Ont.

That plant was excluded from negotiations last fall between Unifor and the Big Three automakers, including GM. The CAMI plant is scheduled to have its own negotiations with its roughly 3,000 workers later this year.

"This decision reeks of corporate greed," Unifor's national president Jerry Dias said. "It is not based on sales, it is an another example of how good jobs are being shifted out of Canada for cheaper labour in Mexico, and Unifor will not let it happen without a fight."

Earlier this month, GM announced it would move Terrain production to Mexico from the Ingersoll plant, but boosting production of another vehicle, the Chevrolet Equinox, with the newfound capacity at the CAMI plant.

"It was previously announced with employees that the next generation GMC Terrain will be produced outside of CAMI," GM spokeswoman Jennifer Wright said. "We have confirmed the production location to be Mexico."

In an interview with CBC News, Unifor Local 88 president Dan Borthwick said when the Terrain news was announced, it was the union's understanding that no jobs would be lost in Canada as a result.

"Our understanding [was] that we had sufficient production in the future and we would not be incurring any layoffs," he said. "Within a week or two weeks we get this horrible news this morning that 600 members would be laid off."

GM says it told union

GM disputes that version of events, saying in a statement it "provided Unifor advanced notification of labour impacts related to product changeovers and transition at its CAMI facility."

"We continue to work with our Unifor partners to manage through the adjustment with all measures available to us within the collective agreement," Wright said, adding that the site is expected to remain a three-shift facility "depending on demand for this new generation Equinox."

Asked for comment, Navdeep Bains, Canada's minister of innovation, science and economic development, said the government is "concerned about the impact of job losses on workers and their families and our thoughts go out to those affected."

"We remain optimistic about the strength and future of Canada's automotive industry," Bains said.

'We're uncompetitive," Ambrose says

Speaking to reporters after a caucus meeting in Quebec City, interim Conservative leader Rona Ambrose said the incident speaks to the need for more government action.

"We don't lose jobs south of the border or to Mexico because we don't have free enough trade," she said, "We lose them because we're uncompetitive."

"Whether it's labour costs, or energy costs — people believe that they can't do business and there isn't an environment to do business," Ambrose said.

The move comes against the backdrop of a new administration in the U.S. that has threatened to tear up NAFTA and slap a punitive tariff on companies that make cars outside the U.S. in places like Mexico, which makes about two million cars a year bound for the U.S. market.

The non-partisan think-tank Center for Automotive Research recently estimated that tearing up NAFTA would directly cost 31,000 U.S. auto manufacturing jobs.

With files from The Canadian Press