The chair of the International Trade Committee has written to the secretary of state for greater information on the recent tariff row involving Bombardier.
SNP politician Angus MacNeil, who chairs the International Trade Committee, queried whether the move signalled the US was taking "a more protectionist stance to international trade".
The US Department of Commerce said last month it was imposing a steep 219.63 percent countervailing duty on Bombardier's new commercial jets after it made a preliminary finding in favour of Boeing, which had complained that the Canadian firm had received unfair state subsidies, and was dumping planes on the US market at below-market prices.
Bombardier branded the decision "absurd", and concerns have been raised over thousands of UK jobs, as the company employs some 4,000 people in Northern Ireland. Trade unions have said tariffs could make Bombardier question whether to stay in Northern Ireland.
The effect could be wider too, as the firm in Belfast has an overall supply chain of around 800 firms in the UK and Ireland, according to trade body ADS.
MacNeil has now written to international trade secretary Liam Fox, saying: "Naturally, the decision is entirely prohibitive to trade, all the more so because a plurilateral WTO agreement, to which the US is a signatory, provides for tariff-free trade in civil aircraft and their parts."
He has asked the secretary of state a number of questions over the US decision, including whether the Department for International Trade had discussed the issue with the US government before the announcement last month, and to what extent the decision indicates that the US government "is taking a more protectionist stance to international trade".
Defence secretary Michael Fallon said last month that Boeing was a major defence partner and it was not the kind of behaviour the government expected of the US firm "and could indeed jeopardise our future relationship with Boeing".
MacNeil has also asked Fox when the department will publish its policy on addressing trade disputes.