Limerick manufacturing plant Atlas Aluminium confirmed yesterday that it is to close with the loss of 163 jobs.
Winding down of operations is to take place over the next four to six weeks.
There are also fears for the jobs of 100 employees of South Midland Construction, which went into liquidation on Friday.
And in Co Louth, some 20 jobs are to be lost at a manufacturing plant, Ardee Extrusions, which told workers yesterday it will cease operations at the end of January.
Confirmation that Atlas Aluminium in Limerick is to shut came after two weeks of industrial action by workers at the Dock Road facility.
Workers said they were owed a total of €250,000 in back pay.
The staff also claimed foreign workers at the company, many of whom came from Poland, were being treated unfairly.
Management at the company, which provided parts for the assembly lines of Nissan and Renault, repeatedly denied both accusations.
In a statement released last week the company said it was unable to pay the latest national wage agreement, and said an independent assessor appointed by the Labour Court had upheld this.
Several of Atlas's main customers warned the company last week that unless the dispute was resolved they would have to move their business.
In a statement issued yesterday the company, which has operated in Limerick for 27 years, said it regretted having to close. "The decision to close is due to the loss of substantial customer business contracts which makes the company's operations no longer financially viable."
News that 163 jobs are to be lost at the company is the second blow to the jobs market in the mid west region in recent days.
Last week it was confirmed that almost 100 employees are to lose their jobs when an Erin Foods plant in Thurles, Co Tipperary closes down next year.
South Midland Construction, meanwhile, is to be put up for sale by the provisional liquidator appointed on Friday, Jim McStay.
The bulk of the company's 100-odd staff are currently on suspension. "This week will tell a lot," said Mr McStay, when asked what the prospects for the company were.
SMC, a leading utility and civil engineering contractor, was building a gas pipeline between Castlebar and Westport for Bord Gáis, but that work has now been put on hold.
Separately, Siptu said the decision to cease operations at Ardee Extrusions with the loss of 20 of its members' jobs was "very disappointing".
Accessory products for floor coverings were manufactured at the plant and workers were told these would now be produced in France, closer to the company's main market.