Northern Ireland unions accused Boeing of “corporate bullying” yesterday after Washington threatened a massive import tax on rival firm Bombardier on Tuesday.

The US Department of Commerce proposed a whopping 220 per cent tariff on the Canadian-owned company’s C Series jet — whose high-tech wings are made by subsidiary Shorts in Belfast.

It came after US-based Boeing claimed that Bombardier received unfair state aid from Britain and Canada.

The final ruling, expected in February, would put 4,500 jobs at Shorts and another 9,400 along the supply chain at risk.

Atlanta-based Delta Airlines has signed a deal for 125 of the planes, which are more comfortable, efficient and reliable than the rival Boeing 737.

The issue has put strain on the governing coalition between Britain’s Tory government and the DUP MPs propping it up.

Aerospace union GMB’s Ross Murdoch accused PM Theresa May of being “asleep at the wheel when she could and should have been fighting to protect these workers,” urging her to intervene.

And speaking at the Labour Party conference in Brighton, Unite assistant general secretary Tony Burke said Boeing was “emboldened” by US President Donald Trump’s “America First policy.”

He said: “What is needed is to end this corporate bullying by Boeing,” pointing out that the British government is Boeing’s second biggest customer, with orders of around £4 billion for such equipment as P8 maritime surveillance aircraft and Apache attack helicopters.

Unite Shorts Belfast branch secretary Joe Bowers told the Morning Star: “Both Boeing and Bombardier depend on public money for their existence and survival.

“We have to to defeat Boeing, but we cannot depend on Bombardier to develop the aerospace industry in Northern Ireland.”

Mr Bowers pointed out that over the past 20 years Bombardier has sold off Shorts East Belfast, its Airbus interest and its design office on the Isle of Man, cutting its workforce from 9,400 to 4,500.

Bombardier is subcontracting its IT service at Shorts to IBM, and has closed its apprentice training scheme.

“These are indications of a company that is not committed to Northern Ireland,” Mr Bowers said.

“The C Series has been designed and built in Belfast. It is 10 years in advance of any international competitor. “These are the skills that have to be protected, and they wont be protected by Bombardier.

“Our policy should be an alternative for the future of aerospace in Northern Ireland.”