Jeremy Corbyn has said the Prime Minister must stand up to Donald Trump over the US's decision to impose a 220 per cent tariff on new passenger jets built by one of Northern Ireland's biggest employers.
Theresa May cannot "bet our economic future on a deregulated trade deal with the US", Mr Corbyn said in his keynote address to the Labour conference in Brighton.
It comes after the US Department of Commerce opted to effectively triple the price of new planes made by Bombardier, a Canadian multinational with a major manufacturing base in Belfast, under pressure from the American aviation giant Boeing.
Unions also accused Ms May of being "asleep at the wheel" and said the US Department of Commerce's decision risked thousands of jobs at Bombardier.
Michael Fallon, the UK Defence Secretary, suggested the Bombardier decision could initiate a trade war with the Trump administration over military contracts.
On Mr Trump, the Labour leader said the US President had given a "deeply disturbing" speech to the UN.
"Devoid of concern for human rights or universal values, it was not the speech of a world leader," he said.
He continued: "Our government has a responsibility. It cannot meekly go along with this dangerous course.
"If the special relationship means anything, it must mean that we can say to Washington: that way is the wrong way. That’s clearly what’s needed in the case of Bombardier where thousands of jobs are now at stake.
"A Prime Minister betting our economic future on a deregulated trade deal with the US might want to explain how 220 per cent tariffs are going to boost our exports."
Register for free to continue reading
Registration is a free and easy way to support our truly independent journalism
By registering, you will also enjoy limited access to Premium articles, exclusive newsletters, commenting, and virtual events with our leading journalists
Already have an account? sign in
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies