The TEEU electrical union said that as many as 30 Polish workers employed by ZRE Katowice up to October last year on the construction of the Shannonbridge power station in Co Offaly were paid less than one third of the agreed rate of 19 per hour.

The latest union revelations about cheap foreign labour come less than a week after the ESB and ZRE Katowice admitted that Polish fitters working on the ESB's Moneypoint station were paid below the legally enforceable rate of 19 per hour. The revelation will also heap more pressure on Minister for Enterprise Micheal Martin to introduce tougher worker protection laws at the national pay talks.

Pat Guilfoyle of the TEEU said at a meeting last Thursday that ZRE Katowice acknowledged it had underpaid its staff. Guilfoyle said that the 63 Polish workers at Moneypoint were now owed an average of 10,000 each.

He added that the union will also be pursuing back money for those who worked on Shannonbridge over the last two years.

A spokesman for the ESB said that the state-owned company was "checking into" claims on Shannonbridge. But he admitted that because the alleged underpayments go back two years, "it could be difficult". The spokesman also said that the TEEU had never raised the issue of underpayment.