Reforms of the work permit system to make it easier for immigrant workers who are being mistreated to change employers are being sought by SIPTU.
In a submission to the Tánaiste, Ms Harney, the union says failure to introduce the changes it seeks would mean an employee was "almost a 'bonded serf' unreasonably and unjustifiably tied to one employer."
As well as the changes to the work permit system, SIPTU wants a mandatory code of best practice for employers, to guarantee fair and equal treatment of non-EU migrant workers and their integration into the workforce and society.
Its two-page submission says integration measures are necessary "to break down barriers between Irish and immigrant workers, avoid ghettoisation and promote healthy levels of integration, thus combating racism and xenophobia."
The union's regional secretary for the midlands and south east, Mr Mike Jennings, said many cases of exploitation and mistreatment of migrant workers had been exposed by the union in recent years.
"Even in relatively good employments, immigrant workers are isolated and do not get any opportunity to mix with the workforce or integrate into the local community. We believe that an employer who recruits workers from abroad should be obliged to have regard to their welfare as people and not just treat them as 'production operatives.' "
The changes sought by SIPTU include clear procedures to allow replacement one-year work permits to be issued if workers have been unfairly dismissed and have another job offer, or are simply offered a better job. Under the current system, work permits are issued to employers rather than to the employee.
Nationals of states outside the European Economic Area - the EU countries plus Norway, Liechtenstein and Iceland - need work permits or work visas to take up legal employment in the Republic.
Officials from the Department of Enterprise, Trade and Employment insist that the current work permit rules do not amount to a system of bonded or tied labour.
"The Department changes work permits for employees wishing to change employer as a matter of course because it realises that not every employee/employer relationship will work out," said one official.
"We facilitated such changes at a rate of approximately 50 per week last year and about 70 a week this year."
Out of approximately 20,000 work permits issued this year to date, 2,000 involved people changing employers, 8,000 were renewals and 10,000 were first-time permits.
Just under half of some 36,400 work permits issued last year were renewals, which indicates stability within the immigrant labour market.
About 2,600 work permits issued last year involved people changing employers.