Power plants, multinational companies and building works across the country could be brought to a standstill within weeks as electricians backed an indefinite strike.
Electricians voted 94pc in favour of industrial action in a dispute over pay.
The TEEU, which represents 6,500 electricians working for a number of contractors, yesterday served notice of industrial action on all electrical contractors for Monday, February 24.
The indefinite strike action will be taken "nationally against all employers simultaneously or strategically against individual employers" in a plan yet to be agreed by the union, TEEU general secretary Eamon Devoy warned.
The union is seeking a 4.9pc pay increase, which it says was recommended by the Labour Court in 2009 but never implemented. This would push the electricians' hourly rate of pay to €24.66. However, the union says that the Electrical Contractors Association, which represents the larger electrical contractors, is looking for a 10pc cut in pay, which would see rates drop to €19.34 per hour.
"Now, just as the economy shows signs of recovery, they want to impose pay cuts," said Mr Devoy.
He said that the strike would hit all sectors including construction projects, energy supply and multinationals, which use electrical contractors.
One of the largest electrical contractors in the country, Mercury Engineering, employs over 1,000 electricians at the Intel site in Leixlip, Co Kildare. Though Mercury is understood not to be seeking a 10pc pay cut, it could still face pickets by the end of the month.
Tom Parlon, director general of the Construction Industry Federation, said the strike threat would create uncertainty for foreign direct investment companies at a time when the country was struggling to get out of the recession.
Mr Parlon claimed that the electrical contractors and the TEEU had reached agreement in 2012 to allow individual employers to cut wages by 10pc.
This was to be included in a new Registered Employment Agreement (REA), said Mr Parlon, which has set pay and conditions in the electrical contracting industry for the last 25 years.
However, last May, the Supreme Court struck down REAs as unconstitutional and as a result many of the smaller electrical contractors imposed pay cuts.
The larger contractors then sought the pay cut as they were being undercut by the smaller operators.
Both sides are to attend a scheduled meeting on Monday when the strike threat is likely to be top of the agenda.