FG Wilson has warned there would be more redundancies as the company prepared to transfer some of its production of small diesel generators to China.
The warning came in the wake of the loss of 760 jobs at one of its main manufacturing firms.
The job losses were announced yesterday as the power sharing executive met at Stormont to discuss the worsening economic crisis amid demands on London to agree to lowering corporation tax in a bid to attract new investment.
Larne, Co.Antrim, will be hardest hit, but jobs will also go at three other sites in the greater Belfast area by the end of the year.
FG Wilson is part of the international Caterpillar corporation and employs 3,000. It more than doubled its pre-tax profits to £7.8 million last year.
But in a statement it claimed the redundancies were an attempt to make the business more efficient and competitive.
Production of 70% of small generator sets is due to be relocated to China by early 2014 which will mean another reduction in the labour force.
The 760 includes 170 who were notified in June that they were no longer wanted, but the scale of the additional cuts shocked the unions and executive ministers.
Northern Ireland's unemployment rate of 8.2% is the highest of any region in the UK.
Robert Kennedy, the company's Northern Ireland operations director, said: "We understand these decisions will be difficult for the lives of many of our workers and their families, and we genuinely regret that.
"We are striving to reduce some of the impact by offering an enhanced VR package.
"We'll also help redeploy displaced workers by providing training on new skill sets, partnering with potential Northern Ireland employers to host job fairs and hiring a placement service."
The company announced in June that it was moving production of its 400 series generator sets to Tianjin, China, in order to build the product closer to its growing customer base.
Mr Kennedy added: "We realise the announcements we're making affect a company that has a rich history in Northern Ireland.
"However, given our current structure and economic environment, portions of our portfolio are not competitive, and we need to react accordingly for long-term growth and to compete for industry leadership.
"Caterpillar is committed to building the remaining business in Northern Ireland and to working closely with local government, including Invest Northern Ireland, as we're focused on keeping it competitive and sustainable for the future."
The enterprise minister Arlene Foster said it was a devastating blow for the workers and their families, but revealed she had received a written guarantee from Caterpillar of the company's long-term commitment to Northern Ireland.
Union leaders claimed the knock-out effect on local business would be massive, and claimed the company acted without concern.
Unite regional secretary Jimmy Kelly said he was furious.
He said: "The company has once again thrown industrial relations guidelines back to Victorian times.
"Our members are spitting tacks at the way they are being treated.
"The high-calibre job losses are a crushing blow to the East Antrim area and Northern Ireland.
"The company has not given its workers or their union representatives the opportunity to negotiate a plan which would have attempted to keep some of the affected workers employed."
The Treasury is under pressure from all sides in Northern Ireland to lower the main rate of corporation tax of 24% and bring it into line with the Irish Republic's 12.5% in an attempt to compete better for overseas investment.
The issue was raised today when the First Minister Peter Robinson met with the new Secretary of State Theresa Villiers.
The CBI said it was vital for the future of the economy.
Northern Ireland chairman Ian Coulter said: "The urgency for securing a lower corporation tax has never been so great in order to maintain our competitive edge and our Executive must win this argument."