Labour and Sinn Féin clashed at the Forum on Europe with Pat Rabbitte strongly rejecting a claim by the smaller Dáil party that his views on migrant workers were intended to appease racists.
Addressing forum delegates at Dublin Castle, the Labour leader reiterated his view that restrictions on some immigrant workers were needed in order to minimise displacement of Irish labour.
Last October, Mr Rabbitte welcomed a Government decision to require work permits from Bulgarian and Romanian workers when their two countries join the European Union in January.
"It is acknowledged that the number of people coming to work in Ireland from the new accession states, or from four or five in particular, has far exceeded predictions," he said yesterday.
He added that, "in the context of circumstances where the member states generally didn't throw open their borders", it was prudent for Ireland to do what he suggested a year ago and introduce restrictions on workers from the latest accession countries "for an interim period".
"The phenomenon has to be managed patiently. Inward migration is a completely new phenomenon for Ireland and the focus, it seems to me, has been entirely too much on the labour market situation, on welcoming a stream of generally well-educated young people, in many cases as a source of cheap labour.
"There is no point in us putting our heads in the sand, there has been exploitation of migrant labour in this economy," Mr Rabbitte said.
"I know, as do most of my colleagues across all parties who have to do constituency clinics and so on, that, on a micro basis, there has been some displacement."
Irish people with very limited educational opportunity could in the past expect to progress to certain types of employment, if they got second-chance education, but that was no longer available.
"That's one of the facts of life we have to live with, because the upside is very positive. The new diversity and energy that has been brought to, not just the economy but the society, is tremendously encouraging for the future."
He said the Sinn Féin delegate to the forum had "entirely inappropriately" accused his party of appeasing racists on this issue.
Mr Rabbitte was responding to comments from Sinn Féin delegate Daithí Doolan who accused the Labour Party of a lack of "international solidarity" and appeasing "racist voices" in its policy towards workers from the new accession states, Bulgaria and Romania.
"My own view is that the Labour Party have unfortunately taken this position to appease more vocal, xenophobic or indeed racist voices in our society," Mr Doolan said.
In his opening address, Mr Rabbitte called for a climate change protocol to be attached to the EU constitutional treaty which could be put to a second referendum in France and the Netherlands in revised form.