Speaking at his union's annual conference in Dundalk yesterday, Owen Wills, head of the 40,000-strong TEEU electrical union, said: "one of the inspectorate's worst practices that must end is phoning up employers in advance to tell them to expect a visit. This may make for a cosier relationship with the employers concerned, but is self-defeating in terms of workers' rights."

Earlier this year, investigations by the TEEU revealed that Serbian workers employed on the ESB's 3 billion upgrade of its network were being paid 4.96 an hour when they should have been paid the going rate in Ireland of 19.97. The Serbians were employed by Energo, the Serbian state electrical company, which was one of the sub-contractors on the ESB job.

The union investigation also revealed that the Serbian workers had to pay their Serbian trade union back home a monthly fee to land and keep the job in Ireland.

Unions in the former communist bloc countries were, and to a large extent still are, state-run.

But the TEEU said that an investigation by the labour inspectorate here happened too late and was ineffective, and as a consequence most of the Serbian workers had since been sent home without getting the millions of euros in wages owed to them.

Speaking last Thursday at the launch of a report by the Migrant Rights Centre of Ireland detailing the increasing abuse of migrant workers in Ireland, Minister of State at the Department of Enterprise, Tim Killeen, said he will treble the number of inspectors to 90 next year.

But Wills said that if the inspectorate continues as it is, "it will not make a bit of difference to exploited workers if the inspectorate has nine, 90 or 900 inspectors".

Calling for specially trained inspectors to be appointed, Wills said the "old emphasis on civil service procedures and pen pushing must end. We need more inspectors on the ground implementing the law, rather than form-filling in offices".

Given the increasing exploitation by employers of vulnerable workers, Wills also demanded that all employers be licensed.

"After all, people need a licence to run a pub, drive a car or own a dog. Surely the social responsibilities involved in employing other people are at least as important, " said Wills.