"It represents an egregious overreach and misapplication of the USA trade laws in an apparent attempt to block the CSeries aircraft from entering the US market", the Montreal-based transportation manufacturer (TSX:BBD.B) said in response to an additional 80 per cent anti-dumping duty.

A second levy of 80% is also being applied to Bombardier's sales to the United States after a preliminary finding that the jets were sold below cost price to Delta Air Lines in 2016.

The US Department of Commerce rulings, which could more than triple the cost of a C-Series aircraft sold into the US, could jeopardise a major order placed a year ago from US airline Delta.

Specifically, Boeing charges that Bombardier a year ago sold Delta Air Lines 75 CS100 aircraft for less than it cost to build them.

"The Commerce Department's approach throughout this investigation has completely ignored aerospace industry realities", Bombardier said in a statement.

The US trade commission is due to rule on the Department of Commerce's 220% tax proposal next year, but ISME said the European Union should not wait for the final decision.

But whether or not Bombardier's jets will face import duties of 300 percent, Boeing may have lost a major sale in Canada. The duty comes on top of a 219.63 percent duty announced last week for "countervailable subsidies" in financing the CSeries aircraft.

To win its case before the ITC, Boeing must prove it was harmed by Bombardier's sales, despite not using one of its own jets to compete for the Delta order.

Mr Turner said: "This latest threat of additional tariffs by the U.S. government, raising to 300% the tariffs imposed so far, highlights an impotence on behalf of a UK Government whose ministers through their inaction appear happy to put Trump's "America first" policy ahead of UK manufacturing jobs".

"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", Ross added.

Boeing says it is the world's largest manufacturer of military aircraft.

The department's preliminary countervailing duty findings agreed with Boeing that Bombardier benefited from improper government subsidies, giving it an unfair advantage when selling its CSeries 100- to 150-seat jets south of the border.

He said workers will fight even harder to get the duty reversed.

"The company is very focused on expanding into Asia, as we see Asia, and India for sure, as the growth engines of the sector", said Francois Cognard, head of Asia Pacific sales at Bombardier, adding this would be its focus region irrespective of how a heated trade spat with larger rival Boeing Co pans out.

Freeland said that Chicago-based Boeing "is manipulating the USA trade remedy system" to block Bombardier's C Series from being sold in the U.S. It was an order of 75 aircraft worth more than USA $5 billion.

Boeing's complaint has prompted a heavy political reaction from the Canadian government and British Prime Minister Theresa May, who fears job losses at Bombardier's wing assembly facility in Northern Ireland.

Champagne warned that "there will be consequences" - essentially repeating Trudeau's threat to cancel the planned purchase of the Super Hornets.