Canadian autoworkers' union Unifor says the massive Trans-Pacific Partnership trade deal announced Monday could mean the loss of 20,000 jobs.

Under the 12-country deal, Canada's 6.1 per cent tariff on imported vehicles will be phased out over five years and domestic content requirements will be slashed.

Auto parts previously needed 60 per cent North American content in order to remain duty-free, with a minimum of 62.5 per cent for a fully assembled vehicle.

But the new trade deal will allow for tariff-free movement of vehicles that have as little as 45 per cent domestic content, which Unifor president Jerry Dias calls "outrageous."