Nearly 4,000 highly skilled workers in Northern Ireland face an uncertain future after the Canadian aerospace company Bombardier put its wing-making operation up for sale.

A spokesman for Theresa May said the government did not expect jobs to be affected, but MPs demanded assurances about the long-term future of one of Northern Ireland’s biggest employers, while one trade union official vowed to “cause hell” if any potential buyer looked like they might cut staff.

In a statement, Bombardier announced the “strategic formation of Bombardier Aviation, consolidating all aerospace assets into a single, streamlined and fully integrated business”.

The company added: “As a result, Bombardier will pursue the divestiture of its Belfast and Morocco aerostructures businesses.”

Bombardier, which recently bought a wing-making programme in the US, has been trying to cut costs at its loss-making Belfast site, major products of which include wings for the Airbus A220.

A spokesman for Airbus said: “While we do not anticipate any impact on A220 production, we will of course monitor the evolution with our partner, Bombardier, to ensure that this is the case.”

Although Bombardier made no reference to Brexit in its statement, efforts to find a buyer willing to invest in the plant could be complicated by uncertainty about tariffs and customs arrangements between the UK and the EU. Airbus, which might have been seen as a potential buyer, has voiced grave concern about the impact of Brexit on its investment in the UK.

Last month, Bombardier signed an open letter to MPs urging them to take a no-deal Brexit off the table to preserve jobs in Northern Ireland.

The company said it did not expect any new workforce announcements as a result of the decision, first reported by the BBC, but the planned sale has raised concern among trade unions and MPs.

Susan Fitzgerald, a regional coordinating officer for Unite, said: “If we see rogue elements and there are people looking to come in and asset-strip, or take a blade to this workforce, we will cause hell if that’s the person likely to be the successful bidder.”

Sasha Wylie (@SashaWylie) “We will cause hell” -Unite the Union say they will be watching who will buy #Bombardier, job security is most important & workers shocked pic.twitter.com/OSkVTLzUyg

A No 10 spokesman said that while the announcement was “unsettling”, the company had a strong order book and further job losses were not expected. The business secretary, Greg Clark, said the plant would be highly sought-after and the government would work with potential buyers.

However, the local Democratic Unionist party (DUP) MP, Gavin Robinson, and Unite both said they had sought assurances that the company would retain its Northern Ireland operations if a buyer cannot be found.

Bombardier said it would look for a buyer that would “operate responsibly and help us achieve our full growth potential”. It promised to work closely with employees and unions during the sale process.

The company’s decision will add more pressure on Northern Ireland’s politicians to restore the power-sharing executive and assembly at Stormont, which collapsed in 2017 amid acrimony between Sinn Féin and the DUP.

The assembly had discussed a plan to lower corporate tax to attract and retain industries before its collapse, said Jon Tonge, a University of Liverpool politics professor and an authority on the DUP. “The fact there is no fiscal autonomy in place – that’s where some of the blame may fall,” he said.

The wing-making factory is one of the final manufacturing giants in east Belfast, a loyalist stronghold that has lost shipbuilding and other industries, costing jobs and sapping confidence in working-class estates. The party’s manifesto boasts its confidence and supply agreement with the Conservative government has secured economic gains for Northern Ireland. “No political party can insure or ensure jobs, but it’s a big blow,” said Tonge.

Bombardier’s announcement came as the DUP was trying to herd voters to the polls in local elections on Thursday. The party’s leader, Arlene Foster, said “both staff and the company can be assured of any support locally or in London which might assist them at this time”.

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Steve Aiken, the finance spokesman for the rival Ulster Unionist party, said the decision made Stormont’s resurrection urgent. “If ever there was a need to get the devolved administration to be back up and running and to support our manufacturing sector, it is now,” he said.

Talks about restoring power-sharing are to start on 7 May. The industry lobby group ADS said Bombardier’s announcement would unsettle the company’s workforce, and the government, industry and trade unions should work together to secure the factory’s future.

“The skills, experience and capability in the Belfast operation means there is every reason to be confident of a positive long-term future for the business and its supply chain in Northern Ireland,” the group said.

In November, Bombardier said it would cut nearly 500 jobs, a decision that followed several previous rounds of redundancies and was said by Unite to “exceed our worst fears”.

Unions called off a strike ballot at the end of April after the company backed away from plans to make some of the redundancies compulsory.