Prime Minister Theresa May and union bosses were stunned when the US Department of Commerce (DoC) decided to impose a tariff on nearly 220 per cent on imports on a new model passenger jet made by Bombardier after Boeing complained the company had been given unfair state aid from the UK and Canada.
The ruling marked a setback to Mrs May’s hopes of a swift UK-US trade deal after Britain leaves the European Union.
The Prime Minister appealed directly to Mr Trump to take intervene in the dispute.
She said she was “bitterly disappointed” with the DoC decision and said Boeing’s long-term partnership with the UK Government was being “undermined by this behaviour”.
Canadian multinational Bombardier is one of Northern Ireland’s biggest employers and the DoC impose tariff has left 14,000 jobs at risk.
Mrs May said: "We are very clear about the importance of Bombardier and the importance of those jobs in Northern Ireland and we will be doing everything we can to ensure that we can see those jobs being guaranteed in future.”
The UK Government said the ruling “could jeopardise” future Ministry of Defence contracts for its aircrafts such as Apache helicopters.
Sir Michael Fallon, the Defence Secretary, echoed Mrs May comments.
He said: “This is not the kind of behaviour we expect from a long-term partner.
“We have contracts in place with Boeing for new maritime patrol aircraft and for Apache attack helicopters and they will also be bidding for other defence work and this kind of behaviour clearly could jeopardise our future relationship with Boeing.”
The Ministry of Defence said: “Boeing's position in this case is unjustified and not what we expect of a long-term partner to the UK.
“Whilst this will not affect our existing programmes, these actions could undermine our future relationship and programmes.”
Mrs May ordered ministers to “engage intensively” with Boeing, the US administration and others to try to resolve the situation.
Allie Renison, head of EU and trade policy for the Institute of Directors told the Telegraph the dispute could be a “take of things to come” when Britain takes back responsibility for trade relations once it leaves the bloc.
She said: “It’s a little unhelpful news at the moment given the US is meant to be our first port of call for trade.
“After Brexit we’ll have to make decisions and be the subject of decisions including from the US on tariffs and we’d have to work out how we’d respond.”
Foreign Secretary Boris Johnson said: "I hope that it can be resolved speedily and obviously we're very disappointed by the result.
“We will be looking at what we can do to ensure free and fair trade to make sure thatBombardier gets a fair crack of the whip.”
Meanwhile, Bombardier said it would fight the “absurd” ruling.
But unions warned the DoC decision was “unlikely” to be overturned by Mr Trump - who has been clear in his aim to fiercely protect jobs in the US.
Russ Murdoch, the GMB union’s national officer, said the ruling was a “hammer bloc” to Belfast and risked sending shock waves through Northern Ireland’s economy.
He said: “Theresa May has been asleep at the wheel when she could and should have been fighting to protect these workers. It's high time she woke up.”