A delegation of workers from Bombardier's Belfast plant will meet MPs on Wednesday (11 October) to urge the government to step up its effort to save 4,000 jobs that are threatened by a trade dispute with the US.
Last month, the US government imposed an import tax of 80% on Bombardier's C Series jets, on top of a 220% tariff already set, after aerospace giant Boeing complained the Canadian company was selling its planes at "absurdly low" prices.
The wings of C Series jets are produced in Belfast and, according to Boeing, any form of aid from the Canadian and British governments amounts to an illegal subsidy.
On Wednesday, Bombardier workers called on Theresa May and her government to do more to safeguard the jobs, after the government was accused of failing to go beyond "fluffy words" to ensure operations at the Belfast plant will not be affected.
"The British government has a duty to defend UK manufacturing jobs against the bullying behaviour of Boeing," said Steve Turner, the Unite assistant general secretary.
"A failure to do so will signal that any ambition ministers have for a coherent industrial strategy is effectively in tatters and that they are happy to put [US President Donald] Trump's 'America First' policy ahead of UK manufacturing jobs.
"Boeing's case is without merit, a fact that Theresa May has herself admitted. May and her government need to be battling for Northern Ireland's Bombardier workforce which makes some of the most technologically advanced wings in the world."
However, business secretary Greg Clark has defended the government's handling of the issue, insisting he warned Boeing that its actions against Bombardier would undermine its chances of securing UK contracts,
"To jeopardise that reputation and relationship by doing something that's completely unjustified is something that I don't regard as being in the strategic interests of Boeing and I said that in terms," he said.
Bombardier is one of the largest private sector employers in Northern Ireland, with operations spanning across four different plants, and May spoke to Trump on Tuesday night (10 October) to discuss the issue.
Workers are expected to urge her to summon a meeting with her Canadian counterpart Justin Trudeau, the unions and Boeing executives.
The impasse surrounding Bombardier is a major headache for the PM, who had repeatedly stated Britain and the US would enjoy a "special relationship" as the UK looked to strengthen commercial ties with the world's largest economy in the lead-up to Brexit.
Furthermore, May has a key alliance with the Northern Ireland-based Democratic Unionist Party (DUP) to support her minority government in Parliament and, last month, the PM called on Trump to intervene in the trade dispute following pressure from the DUP.