Martinrea International Inc. says it will be forced to close an automotive factory when General Motors winds down production at its Oshawa assembly plant next year in one of the clearest indications of the knock-on effects of the closure on suppliers.

Rob Wildeboer, executive chairman of manufacturer Martinrea, says the company will have no choice but to end operations at its Ajax, Ont. plant and offer relocation to the 77 people who work there because the site is entirely dependent on GM's Oshawa assembly line.

The closure of the Oshawa plant and the nearly 3,000 jobs that will be lost have raised concerns of ripple effects through the supply chain, with Unifor estimating every job represents seven spin off jobs in the local economy.

Parts manufacturers and other suppliers have, however, downplayed the overall impact of the closure thanks to diversification efforts after the global economic downturn that helped lead GM into bankruptcy.

Automotive manufacturer Linamar Corp. says it expects to see minimal to no impact from the closure since most of its GM parts are exported to assembly plants in the U.S.

Smaller operations have also diversified, including packager Tec Business Solutions, which says it has reduced exposure to the automotive industry while still having faith in its long-term strength.