SIPTU has accused employers in the construction sector of engaging in similar activities to those that have caused huge controversy at Irish Ferries.
The trade union movement is refusing to engage in the partnership process as a result of Irish Ferries' move to replace its existing workers with cheaper labour from eastern Europe.
The Irish Congress of Trade Unions says this is part of a "race to the bottom" in the jobs market, with pay and conditions being eroded in the name of competitiveness.
SIPTU says this is most obvious in the construction sector, with agency workers and sub-contractors being used by some employers to "displace" existing staff.
The union also claims non-national workers in the building trade are being falsely categorised as self-employed so bosses can ignore agreed pay and conditions.
SIPTU spokesman Eric Fleming said the Government and employers needed to stamp out such activities or construction workers would be forced to take industrial action to protect their jobs.