A Cork SIPTU official has called for the transfer of work permits for non-nationals from employers to employees to help end abuses.
The call came from Mr John Flavin who claimed that six non-national workers in Cork city have been grossly abused by their employer recently.
Mr Flavin said the workers with visa work permits in the service industry came to the union's Cork city offices.
They claimed they were made to work 70 hours a week and were not paid the minimum wage.
"Their employer had not paid them for several months and when wages were finally paid, they each received €130 a week and were living in substandard accommodation," Mr Flavin said.
Mr Flavin said this was one of a number of cases brought to the union's attention in Cork and other Irish cities in the past two years.
He believes many more workers who are being exploited are too afraid to come forward, fearing they will be sent back to their countries of origin if they complain.
Mr Flavin called on the Tánaiste, Ms Harney, to transfer work permits to employees in line with the enlargement of the EU.
"The current system is nothing short of a form of indentured slavery as migrant workers are tied to their employers who hold their work permits," Mr Flavin said.
A spokesman for the Tánaiste said: "Existing policy and practice in relation to the granting of work permits to employers has the safeguard that the employee is coming to fill a specific vacancy, and guards against the person experiencing a period of unemployment.
"If we were to move to a situation where a work permit was given to the individual employee, we would in effect be giving an authorisation to come to Ireland in search of an employer. Such a system is not impossible but it does give rise to a number of serious policy questions."