The Technical, Engineering and Electrical Union (TEEU) says it has prevented five workers from being sent back to Poland by a company accused of underpaying its workers.
ZRE Katowicz (Ireland) Construction is one of the main subcontractors at ESB power station at Moneypoint.
The TEEU says one of the employees due to be sent home was part of team of "whistle blowers" who revealed that the Polish workers were only earning €5.20 an hour on the €350 million refurbishment.
Everyone is disgusted at the action taken by the company TEEU Regional Secretary Pat Guilfoyle
Under the registered employment agreement the workers were entitled to earn €18.97, plus premium rates for overtime.
The union said it only became aware this morning that the men had been given notice that their employment had been terminated and that they were due to be flown home from Shannon, via London, shortly after 5pm.
TEEU Regional Secretary Pat Guilfoyle said after successfully intercepting the workers that, "As far as the union is concerned this is a straight forward case of victimisation of trade union activists."
Mr Guilfoyle said: "We have now secured a commitment for Lurgi-Lentjens, the main contractor on site that it will give an instruction to ZRE Katowicz that the right of these men to remain in Ireland must be respected."
The ZRE workers are due to meet in the morning to hold a strike ballot over the company's actions.
There is also strong support among workers in Moneypoint power station for the sacked workers and TEEU shop stewards are meeting tomorrow to assess the situation.
Mr Guilfoyle said: "Everyone is disgusted at the action taken by the company. Last week ZRE began putting pressure on Polish employees to sign new contracts. We advised them not to do so because they are covered by a collective agreement."
"On Friday the company notified our shop steward and four other union activists that they were no longer needed."