UK Prime Minister Theresa May has said aircraft maker Boeing is undermining its relationship with the government following its dispute with Canadian rival Bombardier, which has seen the latter slapped with 220% punitive tariff on a deal to supply US airline Delta with its CSeries aircraft model.
The US Department of Commerce ruling - earlier this week - could triple the cost of a CSeries aircraft sold stateside, and may jeopardise the $5.6bn (£4.15bn) Delta deal for up to 125 of the jets, wings of which would be made in Northern Ireland.
The punitive tariff came after Boeing complained that Bombardier was receiving "unfair state aid" from the UK and Canada.
However, Bombardier said the decision was "divorced from the reality about the financing of multi-billion-dollar aircraft programmes" and that Boeing is seeking to use US trade laws "to stifle competition."
For its part, the UK government, which passes its legislative agenda with the assistance of Northern Ireland's Democratic Unionist Party, fears the dispute threatens up to 1,000 jobs at Bombardier facilities.
Having previously, expressed her disappointment at the development and lobbied US President Donald Trump to intervene, May said on Thursday (28 September) that Boeing was not adopting "the sort of behaviour we expect from a long-term partner".
Speaking at a Bank of England event in London, May also said there was a wider issue of protectionism rearing its head.
"I think there is a real challenge for us globally today, because I think that there are aspects of protectionism creeping in around the world. But, I want the UK to be a global champion of free trade."
In 2016, Boeing won a contract to supply 50 Apache helicopters to the British Army, which could potentially be scrapped. The US aircraft maker has not commented on the development.