Canada's foreign ministry said Boeing was "manipulating the US trade remedy system" to keep the CSeries out of the country.
USA authorities and Boeing are accusing Bombardier of "dumping", that is, taking advantage of British and Canadian subsidies to sell below cost its C-Series jet.
"We will continue to verify the accuracy of this decision, while (doing) everything in our power to stand up for American companies and their workers". That's in addition to existing 219.63% duties announced previously, bringing the total penalties on imported aircraft up to almost 300%.
Clark also pointed out that Boeing did not manufacture a competing aircraft in the CSeries category, and establishing any detriment to Boeing was seemingly "impossible".
Commerce said it based Bombardier's preliminary dumping margin on adverse facts available (AFA), because Bombardier failed to provide the information it requested.
"It represents an egregious overreach and misapplication of the US trade laws in an apparent attempt to block the CSeries aircraft from entering the USA market", the Montreal-based transportation manufacturer said in response to an additional 80 per cent anti-dumping duty. The Canadian government can also take the case to the World Trade Organization in Geneva.
The Commerce Department proposed a 79.82 percent antidumping duty after a preliminary finding that the jets were sold below cost to Delta Air Lines in 2016.
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Under worldwide rules, unfair subsidies from governments can take the form of grants, loans, equity injections, tax breaks and production contributions, if they give a company or an industry an unfair competitive advantage over foreign rivals.
The punitive tariffs will now have to be approved by the US International Trade Commission (ITC) early next year.
But whether or not Bombardier's jets will face import duties of 300 percent, Boeing may have lost a major sale in Canada.
Clark said: "We consider this action by Boeing to be totally unjustified to be unwarranted and incompatible with the conduct that we would expect of a company with a long-term business relationship with the United Kingdom". The firm order for 75 aircraft had a list price of US$5.6 billion, although large orders typically secure steep discounts.
Some 4,200 workers are employed by Bombardier in Belfast, with around a quarter of those jobs dependent on the C Series wings in questions. He is likely, as his International Trade Minister Francois-Philippe Champagne suggested last week, to send the "strong message" that "Boeing has not demonstrated to be a trusted partner" with Canada.
Canada has threatened to cancel the planned purchase of 18 Super Hornets to temporarily augment Canada's aging fleet of CF-18s.