Under the deal, Canada's 6.1 per cent tariff on imported vehicles will be phased out over a five-year period.
And domestic content requirements — rules that dictate what percentage of a vehicle or auto part must be made within the TPP in order to be sold within the region tariff-free — will be slashed.
Under the North American Free Trade Agreement, or NAFTA, an auto part needed to contain 60 per cent North American content in order to remain duty free.
For a fully assembled vehicle, the minimum content requirement was 62.5 per cent.
The new trade deal will allow for the tariff-free movement of vehicles that have as little as 45 per cent domestic content.
"It is outrageous that the Harper Conservatives have signed a deal that would allow the majority of a car to be made in China, yet still come into Canada tariff-free," Unifor's national president Jerry Dias said in a statement.
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