Siptu's general president has warned that any effort to introduce a 12-month pay freeze and 30 per cent cut in entry rates for construction workers would turn building sites into "battle grounds".
Jack O'Connor was responding to a call by Tom Parlon, director general of the Construction Industry Federation (CIF), for cutbacks in worker costs.
Mr O'Connor said proposals such as those from the CIF, were "neither morally justifiable nor economically advisable".
"The construction industry is not exposed to international competition in the domestic market. To suggest that earnings, which are already less than the industrial average, should have their pay reduced by 30 per cent in order to sustain the profits at the levels to which employers have become accustomed is nothing short of contemptible."
Labour Party spokeswoman on finance Joan Burton called on the Government to reject the CIF call and to ensure that it forms no part in talks on the national wage agreement.
"The effort by the CIF seems to be part of a concerted attack by employers on measures designed to ensure minimum standards and pay and conditions across a number of sectors. "
"The Government must reject these moves and defend the principle of basic pay and conditions for all workers", she said.