Trade unions are struggling to cope with the volume of complaints they are receiving from migrant workers about their treatment in Ireland, a May Day rally was told at the weekend.
Siptu official Eric Fleming, co-ordinator of the event in Dublin on Saturday, said non-national workers were converging on union halls every day.
Embassies were also in frequent contact with unions to seek assistance on behalf of migrant workers, he said.
"Rights and entitlements for migrant workers" was the theme of the rally, which was attended by about 400 people, half of them Turkish employees of Gama Construction.
The company has been under scrutiny because of allegations, initially made by Socialist Party TD Joe Higgins in the Dáil in February, that it has been underpaying its Turkish workers and making them work 80 hours a week.
Gama, a multinational construction company with headquarters in Turkey, denies the claims.
Mr Fleming told the rally participants, who gathered outside Liberty Hall after marching down O'Connell Street led by the Ballymun Munch Samba Band, that migrant workers' difficulties did not start with Gama.
"For many years now migrants have been invited into this country to help us with our economy and they have not been treated properly."
"We have 50 dog wardens in this country paid by the State to look after animals' rights. But there are still only 21 labour inspectors," he said. Minister for Enterprise Micheál Martin recently announced that 10 additional inspectors are to be appointed.
Mr Higgins, who addressed the rally, said trade unions also had "sharp lessons" to learn from the Gama case.
"Very good work has been done by trade union activists, but the trade union movement as a whole has been slow in waking up to the dangers posed by this new situation of abuse of migrant workers."
Patrick Maphoso, a South African and member of Residents Against Racism, said an employers' representative had said on radio on Saturday morning that everything was "hunky-dory" in Ireland.
"I am here to tell him that he was speaking from his Mercedes Benz and that everything is not hunky-dory."