The opposition has warned the decision is an abandonment of Ireland's neutrality
The Dáil has voted join a new EU framework agreement that will see greater military cooperation between member states.
The decision to join the Permanent Structure Co-operation (PESCO) was passed this evening by a margin of 75 votes to 42.
The pact is seen by many as the first step towards the establishment an EU army.
A number of TDs have voiced concerns the agreement will undermine Ireland’s neutrality – while People Before Profit has warned it is considering mounting a constitutional challenge to the decision.
The Taoiseach has claimed the country's neutrality will not be affected – as the vote only opts in to certain parts of the agreement.
He said it would see countries sharing information and co-operate on issues of defence.
However, a host of opposition TDs warned that the Government had tried to “ram it through” the house without proper debate.
People Before Profit TD Richard Boyd Barrett called the vote was an “abandonment of our neutrality and is unconstitutional and should be challenged.”
“No doubt you have been briefing the media that there is nothing to see here,” he said.
“That this isn’t relevant, it is not significant - there are no legal implications.”
“But the truth is, this is us joining up in a common defence which will require us to regularly - and I am quoting – ‘increase defence budgets in real terms to meet the 2% of GDP benchmark.’”
“That would mean a quadrupling of Irish defence expenditure.”
Independent TD Clare Daly said the decision to rush through the vote was an “effort to avoid democratic scrutiny” by the house.
“It is nothing more than a manoeuvre to precisely avoid effective scrutiny of this measure, not just in this House but among the broader public,” she said.
“There is no doubt in my mind this is happening because the political establishment has learned the lessons from the last time people got information - Lisbon and so on - so it is better that we keep them in the dark.”
“If the Government is so confident it can stand over the arguments and answer the questions on this issue, why are we ramming it through today? “It has not been answered and I think the silence itself is the answer.”
The Tánaiste Simon Coveney said the agreement would only commit the country on an, opt in or opt out basis.
“It is no more or less than that on a case-by-case basis,” he said.
“I suspect we will want to use this in terms of counter-terrorism; in terms of peace keeping and training; in areas potentially like marine surveillance – so that Ireland can be part of collective initiatives.”
Yesterday the Taoiseach said Ireland will not be buying aircraft carriers or fighter jets' under the plan.