An MP has accused some employment agencies of scouring Eastern Europe for cheap labour at the expense of the poorest Welsh communities.
Adam Price MP says workers cannot survive on low wages
Plaid Cymru's Adam Price said the effect was to push down wages.
He told BBC Wales' Dragon's Eye those agencies were using migrant workers to improve their profit margins.
Wales has become home to thousands of economic migrants from Eastern Europe recently and Llanelli and Wrexham are towns with growing Polish communities.
They employ Polish migrants mainly in the food processing, retail packaging, agriculture and construction industries.
Mr Price, the MP for Carmarthen East and Dinefwr, said: "It certainly is the case that there are employment agencies working in Wales that go about using the source of cheap Labour as they see them and importing them into all parts of Wales in order to improve profit margins."
He told Dragon's Eye: "There is evidence of a downward pressure on wage rates.
"Workers have been edged out because they simply cannot survive on the low wages being paid out."
He added: "Part of the problem with migrant Labour or economic migration is that the benefit and costs are distributed unequally.
"The middle classes benefit from cheaper services, for example plumbers, but ultimately local people can lose their jobs because of this competition from people who are prepared to accept lower wages."
During the Welsh affairs committee meeting this week, Jeff Hopkins from the Polish-Welsh Mutual Association said that the "problems of the exploitation of workers still remain and that may be political."
He added: "We highlight the zero-hour contracts which are the basis of all their ills.
"The way employers operate is vicious and callous with no consideration for the people who work for them. And I've got to say there are no foreign people involved - Welsh people are exploiting them"
However in a statement, the Recruitment and Employment Confederation, who speak on behalf of the industry told the Dragon's Eye programme that migrant workers "play a positive and important role - they are not cheap labour".
Dragon's Eye is broadcast on BBC 2W at 2100 GMT on Thursday and on BBC 1Wales at 2235 GMT.