Unions representing airport workers are to meet on Monday to consider their response to Government plans to break up Aer Rianta.
The Minister for Transport said earlier the State authority would be broken up into three competing independent companies to run Cork, Shannon and Dublin airports.
Leaders of the Trade Union Federation, which comprises representatives from SIPTU, TEEU, Mandate, IMPACT and AMICUS, have warned that the break-up plans pose a "major threat" to the new national agreement Sustaining Progress. The five unions represent more than 300,000 workers.
Some unions, such as the TEEU, have already threatened to take industrial action if the Minister goes ahead with breaking up Aer Rianta.
SIPTU Vice President, Mr Jack O'Connor, described Mr Brennan's proposals to as a "reckless piece of institutionalised vandalism".
"The decision will have the most far reaching and negative consequences for jobs and standards of employment, in all three locations and will dramatically reduce the value of this profitable national asset which should be allowed to claim an essential role in maintaining the economic independence and prosperity of the people of Ireland," Mr O'Connor said.
He called on the Government to allow the proposals to be evaluated in an "objective process" of consultation.
TEEU regional secretary Mr Arthur Hall, who represents technicians and engineering staff operating the airstrips, said the group of unions would consider its position very carefully on Monday.
"Last Thursday Congress endorsed an emergency motion signed by five of the largest and most powerful unions in the country, to support workers at Aer Rianta in any action they may have to take to protect Aer Rianta. It appears the Minister for Transport is deliberately putting it up to us," Mr Hall said.
He added: "This is economic madness. It is going to cost the taxpayer huge sums of money. The debts transferred from Shannon and Cork to Dublin will damage the latter and the other airports have no long term future without Dublin. This will mean massive job losses not just at the airports but in the regions they serve."
